Oh yeah another question:
This rule goes for mental an social stress tracks too, right?
The rules are the same for any and all stress tracks.
As for stunts granting additional consequences:
A Stunt can grant
one consequence of a particular type that be used in any circumstance.
A Stunt can grant
two consequences of a particular type if their use is somehow restricted. Like maybe mental consequences that only work against torture and or attemts to extract information from you.
If the circumstance is enough of a restriction is up to the gm.