Light exercise at four days after your surgery is fine, moderate to heavy exercise should have a longer waiting time. The only concern would be wearing a helmet, which generally you should wait two weeks to do. A light hat or scarf so the sweat doesn't accumulate (or if you are able to ride...
After two weeks using hair fibers/thickeners is generally considered fine to do. I'd check with your doctor first though, in case there are issues specific to your case that may alter that waiting period.
One of the reasons that beard and mustache transplants are possible is because facial hair, particularly hair that grows around the chin, is actually quite similar to the hair that grows on the back and sides of the scalp. Body hair, however, is distinctly different. All hair follicles follow a...