Definitely. Sabrina originated in Archie Comics and has had various storylines and appearances within that comic series. Her presence adds a touch of magic and mystery to the Archie Comics world.
Yes, Riverdale is based on the Archie comic. It takes inspiration from the characters and settings of the comic but adds its own modern twists and storylines.
It depends. Older and limited-release Archie comic books might have significant value, but common ones usually don't fetch a high price. The condition of the comic and its popularity at the time of release also play a role.