Mustn’t (must not) - used to indicate something that is prohibited or not allowed.
Rule: must + not = mustn’t
Example: You mustn’t smoke in this area.

Can’t (cannot) - used to indicate that something is impossible or not allowed.
Example: I can’t go to the party tonight because I have to study.

Don’t need to - used to indicate something that is not necessary or required.
Example: You don’t need to bring a gift to the party.

Don’t have to - used to indicate something that is optional or not required.
Example: You don’t have to wear a uniform to work.

Didn’t have to - used to indicate that something was not necessary or required in the past.
Example: I didn’t have to take the bus yesterday because my friend gave me a ride.

Didn’t need to - used to indicate that something was not necessary in the past.
Example: We didn’t need to make a reservation because the restaurant was not crowded.