National Electrical Code Articles and Information

1. No. You must use it only in continuous lengths [400.9].

2. Yes. But only for repair purposes, and that repair must meet the criteria spelled out in 400.9.

3. It prevents tension from being transmitted to joints or terminals [400.10]. If you see there is tension, then the fitting and cord are not installed properly.
   
   

4. Yes. You are limited to certain Types. The list is really long, though. It's in 400.11.
   
5. The flexible cord must be at least 18AWG [400.13].