You can pull the HDD out without sliding the board at steps 15 and 16. Quite tricky, but you can.
Really, not necessary.
If you have no such tool, just skip this step. You can pull HDD anyway.
If you skipped step 13, skip this one as well.
You can skip this step with no problems.
I skipped this step with no problems.
If 5.0 mm T8 holes don't line up with those on the body, you should hook the antenna up a bit.