“Can oil pulling reverse tooth decay?”

Depends on how you define "reverse." If you have a cavity that has entered the dentin (part of tooth below enamel), then the pulling is not going to stop the carious process. Pulling will help make your mouth feel cleaner by removing the biofilm that accumulates on your teeth, but it won't reverse the degradation caused by the bacterial breakdown of tooth structure.

Griffin Cole, DDS NMD

Absolutely not.