[Newbies] Re-newbie

[Aidan Gauland]

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