Why do you want to remove it? The only reason would be if you are selling to someone who specifically doesn't want it. But you can get more if you sell it with CFW. Anyway, to answer your questions:
1. No, they'll give you an error if you try to launch them after removing B9S. Remove first.
2. You have to remove it beforehand, it will not work afterward.
3. Yes.
4. Yes, out of region cartridges won't work anymore.
5. I don't know, it might stay.
6. Yes
7. Yes. If you have any custom system titles installed, or if you ever did a region change or changed friend seed or anything of that nature, your console will be bricked after uninstalling B9S.
8. No. You'll have to start over from
https://3ds.guide and on 11.5 this means DSiWare hax (two consoles) or a hardmod.
This is a bad idea. There's a huge number of risks, and removing it solves absolutely no problems. In fact if you are having problems, removing B9S is even more likely to brick your console (B9S is probably what is keeping it functional).