Install stock rom on galaxy s3 through TWRP or dual boot
I bought a used used phone rooted with slimbean on it. I did manage to update through TWRP and really like that rom so far. I'll present an app in a few days and want to use an mhl hdmi adapter to project the app on a screen. It seems there's a driver issue and slimrom wont ever support the adapter. So I need to install the stock firmware for the presentation and want switch back after and would like to keep twrp. I could also dual boot it and that would be even better, but does the stock rom supports it ?
Since I know how to use twrp, that would be the simplest way to install the stock rom, How can I do that ?
Is it possible to dualboot the stock firmware ? How can I do that ?
EDIT: I have a SGH-I747m (canada) and don't know which stock rom I should use, I don't know the original carrier. I looked on sammobile but you need to know your carrier to find it's original rom.