God. Reopening the subject again.

So.. I have my phone SE K550im and I'm thinking about experiencing other versions of software. *W610? which supports Java*
They can't know if I have changed the firmwares between.. a period. Isn't it? The phone is working with any operator, except that it has this special menu and configuration for I-mode.

Can I use a further firmware..or another one and after that to come back to the original? Just asking.. because i'm new in SE domain. *I always was impressed by SE, but I had most of my phones Motorola and Siemens*
What should I do? And what performance is needed?

---- Cosmote Romania (Cosmorom) i've seen they have with ...some ..main and fs? I don't know what's that. :D Sorry.. beginner.