How does mission progress work in multiplayer for Borderlands 3?

This question has been asked for borderlands-2 and borderlands.

I can start my campaign that people can join, and I can join other people campaigns. In all these campaigns I will be at different points in story progression with different side quests completed or available.

How exactly does this work? Will my character do same quests and side quests twice in my friends campaigns and in my own? Is there a difference how main quests and side quests are handled?

I read somewhere that if you join a campaign and do a side quest it will count for your main campaign but only if it was available to you in your own campaign. I'm not sure how that works, how does the game determine if it's available to me or not? If its completion makes another quest "available", what happens then?

If this is true, that players in the same game can have different quest availabilty, how does the game present to the player that cannot do a quest that another player is currently on that quest in terms of objective tracking?

I just finished remnant from the ashes, and in that game the progress is bound to host, that is as far as campaign goes only the host makes progres and your own compaing does not progress. I beleive in Borderlands 3 it works differently. How?

As far as I know from personal experience and from reading stuff it is as following:

Scenario 1: You host a game.

You are at your point of progress regarding main quests and side quests. People who join you, can only do the quests that you have access to, even if they are ahead or behind you in progress.

Scenario 2: You join a game.

You can only do the quests that the host has access to even if you are behind or ahead in progress. Lets say you are behind. If you now complete a few main quests while in the game of someone else, the game will mark these quests as completed for you. If you now go back to hosting your own game, you will still be at the point you previously left. But as soon as you reach the main quest that you already completed in the other game, then you can skip these quests that you already finished.