Is sectioning off a permanent crown with 1 pontic easy for a dentist to do? possible for the pontic to remain for cosmetic purposes for a short time?

It's quite easy: Water cooled high speed handpieces cut through metal very easily. The pontic is attached to the crown (abutment), right? Once the crown is sectioned and removed, the pontic follows. A temporary can be fabricated for cosmetic purposes.

It depends: Sectioning off a crown is relatively easy. If you are talking about ONE crown attached to ONE pontic, this would likely be a cantilever bridge, in which case sectioning the bridge would eliminate the pontic, since the cut is made at the joint of the pontic and crown. The pontic has no other support and would fall off. The crown could stay if there are no other problems with the tooth supporting it

Very easy: and if carefully done, no damage to your live tooth or abutment underneath will occur.

Yes: yes it is easy and yes (in certain cases if it is attached to an other tooth as in a bridge) the pontic may remain for cosmetic purposes. Is it idea, no, but it can be done for a short period of time.