KMS Inner Ability Revamp - Questions

1, 2. I've heard that the Medals only give 3 to 10 Honor EXP post-revamp, so depending on your Honor Level it might or might not be a wise idea to use them before the update.
3. It's pretty similar to the old system, with the addition of line lock (you can choose up to 2 lines to lock) and the ability to circulate after Legendary. There are details about the costs somewhere but I cannot find it right now.

Can't answer 4 but I would assume no because I haven't heard anything about it anywhere.

That's good to know. There's no problem locking Legendary lines, right?
Unless it doesn't cost a lot of points to reset your lines, 3-10 EXP for every medal is pretty low.