It's cool that you're open to learning. Most people don't know that pretty much every bee species is solitary. Social bees are exceptional.
You knew about bumblebees right? Those are solitary bees (most of them, there are colonizing bumblebees as well)
Some are in between! Some carpenter bees will share the same brood tunnel, cooperatively maintaining and enlarging it while individual bees build their own side tunnels for their babies.
Yes, but for some reason I don't think of bumblebees as bees. Irrational, I know!