Album Troubles

So I have few questions all related to a few new albums I have add into my music library recently.

Q1. When I go to put on the album artwork from the pictures on my computer to one of my albums it won't stay. So I'll select the picture I want, click done and nothing happens. I've tried doing it several times and even deleting and putting the album back on iTunes but that doesn't work either.

Q2. On this same album I want to change the album artist to just one instead of a mix of them. I did try and change it but it didn't work and I've tried several times in hope it wold change but it hasn't.

Q3. On a different album, I have 3 versions of it, each with different songs from the one album in it and I have tried changing the album name and the artist to the same one but it hasn't worked to out them altogether.

If you can help out in any way possible that would be much appreciated!