I have 2 questions first,

1. I want to extrude these faces, with keep faces togheter off.. as you can see in the screenshot the faces in the edges in the middle will not extrude, so the faces do keep togheter
In hte video, it gets deselected and then selected again, but i'm not sure which buttons i should press?

2. I have hidden some objects with Alt + H, now I have closed the file, and opend it again.. I can't get them back with Ctrl + Shift + H.. it says no previous hidden objects to show. How can I get them back so i can see them again