Is it permissible to supplicate to Allah to change an event that has already occurred in the past, or to go back in time to correct religious or worldly mistakes, such as a person who studied medicine supplicating to go back in time to study another specialization?

Praying to go back in time is asking for the impossible and is considered an aggression in supplication, which is forbidden by Allah's saying: "Invoke your Lord with humility and in private. Indeed, He does not like aggressors." You can pray that Allah makes your specialization beloved to you or transfers you to another one that you love, without aggression in supplication.