Is it possible to update a game "Over-the-air"?

I am totally unexperienced in video games development but I have many interrogations as I’m getting more and more interested in it.

Can a game that went live can be updated without submitting the update to the platform (steam, playstation store etc.) ? For example, I want to modify the map and add new areas. Can the new assets be downloaded directly from the game and be applied ?

Can I modify assets in real-time as well as adding new missions on a daily basis without submitting the updates each time to steam, psn, xbox live etc. ? If so, How deeply can i modify the game ? Just little things or it is possible to change the structure of the game itself ?

For consoles, no, you have to get updates approved by the platform.
For PC you have the option of building that into your game but you’d need to have your own server to deliver the updates, otherwise you’d have to deliver them through Steam.