That is not true. There is kickstart 3.5 and 3.9 it is even mentioned on AmigaKit.
No, there aren't. There may be
modified kickstart 3.1 roms that some people call 3.5/3.9, but 3.5 and 3.9 DO NOT EXIST. Also, I'd be careful about using these modified roms. They may contain bugs that aren't in the original. Stay clear of those things and use 3.1 roms.