How can i start missions

can you explain to me how to do a mission system such as batman arkham series, spiderman ps4 and other open world action games.
Also, side missions.
Also, how can i start a mission with a cutscene?
And my last question, so when i start a mission and it plays a cutscene, after the cutscene how can i transition the the level to a different part of the game, such as in the spiderman ps4 game when peter and mj have a cutscene, after it, you get to play as mj 3 days before, how can I do that.
Thats it for my questions, please someone respond and THANKS!!!

thats an extremely broad question and there are hundreds of ways to do it.
For something like a “Mission” not only your character but several other objects in your game will be differently affected “such as new enemies spawning, doors being unlocked, etc.” what i like to do for things like this is have an invisible object “Which i like to call a Logic Cube” and have it hold variables that multiple actors will be using

so in your logic cube you can have a boolean called “Mission 1” and when its set to tue, you can have it call events and functions on other blueprints in your game that are affected by it.

For cutscenes, use the sequencer tool to make them, you can make them play in the level blueprint.

and i mean for the last part, that sounds like youre literally just opening a new level in your game, idk how your game is setup, if you have a seperate controller blueprint you can just have it possess a different pawn (like MJ instead of spiderman). if youre not and all input is being handled in your character blueprint, just add a new character in the new level and have it set has the default pawn for that level.

Again, try to be a little more specific with your questions, and try to post pictures of the blueprints you have so far so people know exactly where youre getting stuck. Hope that helped!