French law and changing of jobs (Paris)

Hello all, there's something I'm curious about. I'm thinking of the possibility of changing jobs and I was wondering the legalities of this.

I currently hold a carte de sejour which expires in December, on it, it says that I am "salarie". The company I am currently working in is the company that applied for the work permit for me.

The questions I have are:

1. Am I allowed to have a 2nd job part time? Say at a bar at night / during the weekends.

2. For the renewal of the carte de sejour, what do I need? Must I be employed by the same company as when I first applied for it?

3. For the renewal of the carte de sejour, what happens if I am in between jobs? Does the new company do this for me? Or can I only switch jobs after I receive the new carte de sejour?

4. What if I decide to take a one year break, can I "renew" my carte de sejour a year later? Or do I have to reapply for a new carte de sejour? What if I don't have a company to do this for me? Can I still get a carte de sejour?

Any answers to these questions will be appreciated. Thanks