Depends on the condition of the wood. If it is good, yes, I just remove the old comb and render it. If it is rickety and has wax moth holes in it, I throw it out, or use it for smoker fuel. 
Same answer as above. Just be sure that you are not re-using a frame from a diseased hive (chalkbrood etc). Of course AFB affected frames should never be re-used and I wouldn’t render the wax either, unless it had bee irradiated first.
If you want to be extra-safe, you can scorch the frames carefully with a blow torch before re-using.