What happens at the end of the main quest?

[Hayashi.226]

Where does the story pick up? Just before the point of no return?
Also, are there any side quests, gigs etc that are closed permanently by progressing in Act 3?

 

[Shoklen]

Spoiler

As long as there is a save point right before going into the building/elevator, you will pick up right at that spot with a few extra goodies in your bag (or ripperdoc).

My last playthough I saved the final mission till last then that was the end of that game, and started a new one.