How can i change the tech SWDtech??

if you corrupt the ROM the most that will happen is that your save files will be erased - your computer will not break.

For moves like demon fang and double demon fang, you can use the attack "Shock Wave" as a start. And you need FF6 Miscellaneous data editor (MDE). What you need to do is look for the dispatch attack (which is invisible in the attacks list) and replace the bytes there for the bytes of the shock wave attack.

The closest to the Beast attack is Cyan's Empowerer (Bushido LVL 5), but cyan's attack uses a dragon instead of the lion displayed by lloyd or cless.

For rising falcon, you could use phoenix's sprite and replace it by bismarck's sprite. And when the character attacks, have the phoenix's sprite fly across the screen (zeemis did a similar thing).

As for falcon's crest and sword rain, I have no idea. Good luck with that though.