[Brodsky]

1. This is definitely possible. All you would need to do is have your artist bounce their tracks as a .wav or .mp3. You can then import these files into Pro Tools. I personally prefer they bounce with no plugins on their tracks so I can mix it, but tracks with processing included could be a good reference mix if you're mixing the vocals if they don't know how to. When recording your drum and guitar track be mindful of the bpm they used in their DAW when recording. There will be rhythm issues if you record your instruments on a different tempo than they were using.
2. There are two ways to do this: Create your session as a Project, this will save it on your Avid Master account and can be accessed from any computer running Pro Tools that is signed in to your account. The other way to do this would be to find the disk location of your session on your hard drive and compress the folder containing your session file, wavecache and session backups to a .zip and email it.
3. Pro Tools First is very limited as compared to other versions of Pro Tools. Consider it a Lite version. I don't know what specifically you are referring to but having Pro Tools Ultimate vs. Pro Tools First is a big difference in content.

I hope this satisfies your questions.