halo 3 question?

[Frankie]

okay so i beat the game on normal
now i want to beat it on heroic but do i have to beat the whole missions on herioc or legendary or just the last mission
the question is do i have to beat the game over from the beginning or just the last mission

 

[Joe Flare]

you have to start from the beginning i know it sucks if you beat it on legendary theres an alternate ending and dont forget to watch the ending after the credits

 

[paulwallfan22]

so whats the question u idiot