Question on Copyright laws for screenplay writing and film making?

I am about to write a television series and I have a few questions on
copyright laws.
1) Can I show footage from another TV show in the background or at the
very least can I have audio be heard from it so that people know what
the characters are watching
2) Can I show video game footage on a TV set as characters play a game

3) Am I allowed to have items such as star wars action figures, movie
posters, etc in my show.