What I find amazing is that the literature on the various stages of when we started walking upright and all the transitional appearances of pre-human until what we look now was so well preserved in the fossil evidence that backs this story up as being factual.
Sadly, most creotards would disagree with you there - they propagate lies such as "Lucy was part of a pig's jawbone" or "they made it all up because they had so few pieces". There are some people who seriously believe that "Lucy" is all we have of afarensis, or that it's actually a gorilla or a monkey mistaken for a hominid ancestor.
All the other primate lineages are limited to a few skull fragments with the exception of gorilla's fossils that were never found.
So now...what? Because the human evolutionary line is perceived as being so good, and all others aren't, it's still fake?
I say perceived - ape ancestry is also very well known. You're buying into the same lies as for human ancestry. No, I'm sure they don't have all the pieces, but they do have many. Far more than "a few skull fragments".
I see many changes occurred for our line but our primate cousins hardly changed at all. Can anyone explain this?
I can explain it - you're wrong and they changed a lot. Alternatively, degree of change isn't some marker of importance or of "amount of evolution". There is no real marked "up" or "down", it is mostly sideways at this level. if there were a group of monkeys well adapted to their environment and said environment didn't change for millions of years, I don't see why there would be pressure to change overmuch in a scant few million years. Tens or hundreds of millions is another thing, but even on such long timescales can similarity be retained if the form is well adapted.
In short, I'm not a developmental biologist nor anthropologist, but many of your questions are reasonably trivial to answer and the only reason I suspect you don't know is you haven't asked the right people (or alternatively have been lied to).
Retroviruses on primate lineage showed no connection and they are unique to each primate group. Location of retroviruses may be the same but the retrovirus associated with it is not the same in each primate.
See, this tells me you've been reading
something, but you either don't understand it or it is wrong or misleading. If it's being quote-mined by creationists it is likely you don't understand it because it has been manipulated and is intended to mislead you.
quote your source, let's have a look at it.