I don't think that this is the place to discuss time travel but I am glad that Data, Mr Logic, understands time travel the way I do. One cannot change the past because it has already happened. My mother and I argue about this from time to time. Our fundamental difference in opinion is that she thinks that time has only progressed to this point while I believe that time has already happened completely.
Troi quotes Data's definition of friendship: 'As I experience certain sensory input patterns my mental pathways become accustomed to them. The inputs eventually are anticipated and even missed when absent.' Amusing definition. He obviously misses empathy and sympathy, at least in his definition but he does seem to figure it out in his interactions. Trust and honesty are also important but Data is practically incapable of deception. He can also anticipate the needs of others. I suppose he would be a natural best friend.
"Curious, isn't it, that the world got for such a great, long while with no humans around to fill up space." - the supposed Samuel Clemens (Mark Twain).