oh okay i just google downgrading and lots of thing popped up
but your saying if im 9.2 and above you can downgrade?
Nope, only on 9.2 and lower. And actually, if you're on 9.2, it's pretty useless to downgrade afaik
and for those who are able to downgrade and use 3ds games are you able to play online after even though your not on current firmware
Well, it's possible even on non hacked consoles, if you have the game's latest update installed.
Just keep in mind that:
1) If you download ROMs and try to play online with a public header, it's really likely you'll be banned. You need to get a private header to play games online safely.
2) Some users have reported console bricks using Gateway's mode with the DSTwo+, so be really careful if you buy it. I would personally recommend to only use it for DS games and DS homebrews / emulators, and to install a CFW (RXTools on O3DS, ReiNAND on N3DS) to play 3DS backups.