Steam

Impossible.

Unless you mean irl friends who are accessing your account. But only one can have access to the client at a time, so still impossible

Not possible and i dont think they will ever add something like this.

I read something about some form of sharing being possible further on, but I think that was for big picture mode splitscreen. I might be wrong though.

i saw something some where that said steam users can access their friends games that they aren't playing and play them idk was just wondering

mmmmm steeeaaaaaaaammmmm.

You mean something like this?

Hasn't been integrated yet nor was there any info from Valve if they're going to.