Anyone knows if Fender G-Dec-3 shows the main key of the track?

I don’t believe it does. That’s a difficult technology to fit into a guitar amp.

@dverhey no man, the amp has backing tracks included, and i want to know if it says in wich tone is each backing track

Oh… I see. Still, I don’t believe so after a quick google search. Does it say anything in the manual or the paperwork that came with the amp about the details of the backing tracks given. I think that’s probably your best bet.