Will the AI go for an impossible victory?

Technically speaking, disabling most victory conditions makes even attempting them impossible. Turning off space race makes it so the Apollo Program is no longer buildable. Likewise turning off cultural and diplomatic vortories will disable the Utopia Project and UN respectively. Simply put, the AI will not attempt it because it cannot.

Victory conditions aside, the science, culture, and diplomcay mechanics still provide useful advantages, and the AI will pursue them based on what it perceives to be the best strategic option at the time. The personality of the leader is also a factor, which is why some civs may not seem to be gearing up for battle, or why an aggressive nation will still go to war even if domination is turned off.