I don’t think the version is different at all. Just the delivery system and the way it is encapsulated/suspended. Humans and small animals can get a pill. Farm animals get a paste and possibly a subcutaneous injection (not 100% sure on that). Otherwise, ivermectin is ivermectin - like acetaminophen is acetaminophen whether gel cap, capsule, tablet, or children’s flavored liquid.
You are correct. Ivermectin is a specific molecule. Its chemical formula is C95H146O28. It is this same formula whether used by humans or animals. The body cannot the difference between ivermectin in a pill or a paste. The only difference is the vehicle and the wrapper.
Yep.