The Infallibility of the Pope has nothing to do with issuing commands or excommunicating anybody. Popes have always been capable of abusive governance, and unjust excommunications. Nobody would be restrained, by the Church's teaching on Papal Infallibility, from rebelling .
Setting the date of Easter could not possibly be the subject of an "infallible" decree from the Pope. It isn't dogma or a moral matter.
I didn't say it was, but that it was an early attempt at overreach of the sort which eventually did come into the grasp of office of bishop of Rome.
Regardless of perhaps when the focus is on chair-y, alone as qualification for infallibility , commands, censures and excommunication that come about are demonstration of teachings in a sense, even as they are also enforcements of what is claimed to be 'divine authority'.
That sort of singular authority claims made by anyone, for any one bishop, including the one in Rome, in the beginnings of the wider, thus actually catholic Church, was looked upon as anathema itself...
Orders of excommunication in the past often included condemnation of the alleged heresy AND dire threats for all those who would entertain or agree with whatever set of ideas or propositions were alluded to, with the thundering condemnations including citing Peter and the Apostles, the papal office, etc -- making those sort of excommunications to be very much matters of faith and morals -- fitting the general conditions for notions of infallibility be associated with them, although the canon lawyer types will come up with some argument or another to set aside whatever it is that they may wish to not be looked upon in certain contexts -- only to have others of the Roman church pick up the figurative/rhetorical pitchforks while citing the past (now much 'whitewashed' & for the euceminical minded faithful, much internally/mentally compartmentalized decrees) as weapons used by those RC'ers more polemical than euceminical against those whom disagree with them on some point or another, in efforts to; keep others of the 'faithful' held under under the concepts and words as if they were in effect infallible teaching of the magesterium.
Also as I pointed out, the infallibility mantle lay not only upon the shoulders of whoever is at any one time the Bishop of the Church of Rome...but is spread much wider.
As you demonstrated, in common view it is spread far back into history, even though that cape was not sole province of the Church of Rome, nor sole province of it's bishop in the very times you pointed towards as if it DID reach back to cover those things.
Fr. Nicholas Gruner a priest and Fatima Crusader now under suspension, continues to function as a priest with no further penalty, points to a sea change in regards to attitudes and teachings on faith and moral matters, unless how [Roman] Catholics should view other ecclesiastical communities is not connected to "faith", and perhaps even morals also.
First, he points to the early 20th Century Mortalium AnimosENCYCLICAL OF POPE PIUS XI ON RELIGIOUS UNITY TO OUR VENERABLE BRETHREN THE PATRIARCHS, PRIMATES, ARCHBISHOPS, BISHOPS, AND OTHER LOCAL ORDINARIES IN PEACE AND COMMUNION WITH THE APOSTOLIC SEE. of Pius XI, to then compare that with what has come about since Vatican II.
I could delve into that [above] encyclical of Pius XI from the year 1928, and crack it open around about part 9 where he goes into comparisons of those who believe one thing (a "Catholic thing"?) and those who hold differing view-- and perhaps split the differences in such ways that the gaps are much bridged.
I do not have at the moment, yet another quote at my fingertips which I would at this time dearly love to bring here and provide source for, for it quotes a ranking priest remarking as to there being something of a fresher understanding of Luther's (and generally Anglican views also) on Holy Communion -- those now being seen by more than a few within [Roman] Catholicism to be in effective results so much like how that is understood by those of Rome in this day and age that the difference is negligible -- other than for those who hold the view; that it has to be presided over by a priest 'in good standing' with Rome (no matter how much of a scallywag he may be, in truth).
To THAT sort of thinking (that it has to be a [Roman] Catholic priest presiding) -- the canon lawyers have a ready-made exception for in pointing towards the difference (from Roman Catholic perspective) of "invalid" and "illicit"...
That sort of thing too, is a having things both ways. The Church of Rome has said so many things in so many ways -- it can take either side of many controversial issues, pointing to a this or that while nudging people to "think of it --- like this".
In doing so, it drives more than a few folks semi-bonkers. One needs to tune much of it out, or else learn how to in rather Byzantine manner compartmentalize while engaging in varying cognitive dissonances, with all the little exceptions/limitations/lawyerly technicalities turned on and then off as one would flip a light switch in order to make it all "work".
Reflect again on the previous The Successor of Peter Teaches Infallibly which does include that which is lesser than fully ex-cathedra, dogmatic decree...
Then reflect on guys like Gruner (and hosts of others within Roman Catholicism?) and what Colin B. Donovan, STL here https://www.ewtn.com/expert/answers/fr_gruner.htm says about such persons, their reasons, the surrounding issues, while he notes several things --- part of which I will quote, though I MUST interrupt him part-way thru; Is such a position defensible? In many theoretical ways, yes. Infallibility is not engaged in the conciliar and papal teachings supporting these new directions, ..." "This criticism reached its zenith in 2000 with the publication of We Resist You to Your Face, the "You" being Pope John Paul II. Co-sponsors of this document include Catholic Family News and The Remnant, and traditionalist authors Marian Horvat and Atila Sinke Guimarães. This resistance is intended to restore the Traditional Catholic Faith, as they understand it, by resisting what they see as novelties and innovations in the governance of the Church since Vatican II and in particular under the present Pope.
Whoa! FULL STOP.
What did the The Successor of Peter Teaches Infallibly just say? One paragraph which I quoted previous; For this reason the Second Vatican Council states that all the Pope's teaching should be listened to and accepted, even when it is not given ex cathedra but is proposed in the ordinary exercise of his Magisterium with the manifest intention of declaring, recalling and confirming the doctrine of faith. It is a consequence of the institutional fact and spiritual inheritance that completes the dimensions of the succession to Peter.
Putting things together -- the mantle of infallibility as it can be worn by ORDINARY exercise of his Magesterium.
Turning back to Colin B. Donovan, from the top of the paragraph I previously interrupted; Is such a position defensible? In many theoretical ways, yes. Infallibility is not engaged in the conciliar and papal teachings supporting these new directions, the Pope is not impeccable (sinless), and the possibility of fraternal correction of a pope exists. Added to this are the many abuses going on in the Church which scandalize Catholics and discredit the Council. However, the doctrine of the Ordinary Magisterium, that of Papal Primacy in all matters of governance, the obligation of religious assent and obedience to non-infallible teaching (Lumen gentium 25), the concurrence of the apostolic college of the bishops (both at the Council and since) to the whole body of conciliar teaching and policies, together with the acceptance of the overwhelming majority of orthodox clergy, theologians and laity, argue in favor of the teachings and their application.
See what I mean by a having things both ways? Donovan continues of course...and goes through the reasoning of how the overall thrust of the proceeding must be adhered to (discussion and dissent is allowed -- but only as long as one eventually submits to all which 'Rome' pronounces at any given juncture, regardless).
No thanks.