1) It won't block you choosing to update in the Wii menu.
2) There's still a few.
3) The look the same to be honest, it's the content that's different. Had no major issues with 13, not sure about newer games on 10 with the 002 error.
4) No. Probably a little safer with unskilled hands about.
5) Don't know.
6) Just use wad manager, make sure you have a trusted source of wad files though.
7) If you download a bad wad you can get bannerbricked, hence the suggestion in 6.
8) No idea.
9) See 8
10) See 9
11) Yes, just keep the relevant files on a shadow folder on your computer in case you need them.
12) It uses mIOS.
13) If you want you could have daily NAND backup and store them on your PC. Might be a tad tedious though.