[Newbies] Re-newbie

Hello Squeakers,

It's been over a year since I last used Squeak, so I have some new newbie questions (as well as some old ones that I never really found an answer to) that I have not been able to find an answer to on the web.

1) How do I use/manage ChangeSets effectively? (I never really understood them.) 2) Why has Tweak not replaced Morphic in Squeak? 3) In what ways is Pharo a fork and not just yet another Squeak image? 4) Should I use Cog or just stick with the official Squeak VM from squeakvm.org 5) Why is there a changes file if the image itself is modified?

Thanks, Aidan