I have NO KNOWLEDGE of the 777 FBW system but i assume, it won't let you get close to a stall, let alone a spin.
I wouldn't say the 777 FBW in normal mode will prevent you from stalling, but it certainly drops a heck of a lot of hints on the way to the stall that you are doing something wrong.....
If the FBW has degraded into secondary/direct modes then those hints/protections are absent.