What if you kill the following people before doing their quest: yes man, the colonel at the dam, Caesar, and mr. house, are you stuck in a game with no ending? or is there a way to still finish the game? (i have not done this i just want to know if this can even happen and if it can what follows)

You can't kill Yes Man. He just says, "I'll try harder next time" and jumps into another Securitron.