A.

FFI: None
FFII: Actually, its your first battle with the Black Knights, you fight them, but you can't win.
FFIII: None (not sure correct if wrong)
FFIV: Kain (Cecil fights him in Fabul but he can't win), Golbez(first fight, but when Rydia comes back you can finish him)
FFV: None
FFVI: Pretty sure its Guardian (correct if I missed any)
FFVII: I wanna say Ultima Weapon (you can fight him, but he never dies so its pretty pointless, til you finish him for good.)
FFVIII: None (correct if wrong)
FFIX: Beatrix, Kuja(first fight) (I think, correct if wrong)
FFX: None (correct if wrong)
FFX-2: None (correct if wrong)
FFXII: Not sure so correct me
FFT: None
FFTA: Lenare (I think I spelled his name wrong lol)

Q. What FF games feature bosses that you MUST defeat under a certain time limit?