It is common (or possible) to suffer from sleep apnea if a peson only sleeps on one's stomach or side?

Yes, very common: Sleeping on your side and/or stomach is a survival technique you developed with out even thinking about it.These positions help to open your airway by keeping your tongue more forward and you can sleep better. Unfortunately that may not be enough. You should get a sleep study if you suspect you may have sleep apnea. Undiagnosed sleep apnea is a killer.

Sleep apnea: It is possible to suffer from sleep apnea in any sleep position. While it is often more prevalent when sleeping on the back, someone who is overweight, has enlarged tonsils and adenoids, a deviated septum, allergies, sinus issues, an enlarged tongue, drinks alcohol before bed, can have sleep apnea. Some medications can also add to the problem.