For Blood Sun, do shocklands come in untapped, or is that just a modification of how the enter the battlefield and not affected by Blood Sun?

magicjudge:

While Blood Sun is on the battlefield, all lands will enter the battlefield untapped unless an effect from a nonland source causes them to enter the battlefield tapped.

This is because Blood Sun removes those ETB replacement effects before they can be applied. 

No, you don’t get to choose a creature type for Cavern of Souls or Unclaimed Territory.

Yes, bounce lands from Ravnica and Visions and Mirage are a lot better with Blood Sun on the battlefield.