Some 18650 Li-Ion cells have a protection circuit inside and some do not. I got my name-brand 18650 Li-Ion cells from a laptop battery and the protection circuit was inside the enclosure that held the 18650 cells.
The Li-Po batteries for my RC model airplanes do not have a protection circuit. The protection circuit is in the airplane and in the charger.
The Li-Po batteries for my RC model airplanes do not have a protection circuit. The protection circuit is in the airplane and in the charger.