All you had to do was read
the release page. Despite that:
2.5.2 - adds region free, can boot without bringing up the menu (like gateway), ability to boot to sysnand
2.6 - improved region free, faster emunand booting
3.0 Alpha - Themes, MSET on any firmware from 4.x up to 9.2
GBA support still works, and you don't need to choose between SSB4/MH4U or GBA games, you can have both on one rxtools.dat
You update by replacing rxtools.dat and firmware.bin (get the new one by installing Python 2.7 and running cdn_firm.py in the tools folder)