After failing to get my broken exhaust fixed and I now in the process of fitting a new cat-back exhaust.

The exhaust came with a gasket to go between the pipe and the catalyst. Do I also need to apply some sort of sealant between them ? Also, the exhaust has a join near the back box with a clamp to hold it together, do I also need some sort of sealant there ?
_________________________
Remind me to change my signature to something more interesting someday