If human beings were indeed making and using hand tools 300,000 years ago then I think it’s fair to say that the historic timeline of hand tools goes that far back. Therefore, the term “prehistoric” is not necessarily applicable and since we are talking about beings who developed tool design, fabrication and usage skills then we must also be talking about a historic timeline of people that also goes that far back.
Anything unmeasureable before the Big Bang could be thought of as being prehistoric. But what if there WAS something measureable before the Big Bang?
By normal definition of the word "history", it began when people themselves began writing, circa 3,200 BC.
Everything before that is classified as "pre-historic".
"Pre-historic" doesn't mean we know nothing about those folks, just that we have no written records which they themselves left.