Sorry I skipped right over your other questions. If it's M. baumii it will have yellow, very light citrus-scented flowers. Generally in the spring, sometimes in the fall (fewer flowers).
You can sow the seeds, I have had good luck with Dolichotheles.
It's a pretty standard cactus, care-wise. Give it as much sun as you can, water it when it's dry, feed it occasionally.
Depending on where you live (I'm in Arizona) keep it away from frost in the winter. They go somewhat dormant in the winter, but given enough sun and warmth it will grow slowly in the winter. During the warm months it grows fairly quickly if you keep it watered. If the tubercles get wrinkled it's past time to water.
As a matter of personal style I put small gravel on the soil (top dressing) to keep moisture in. And I generally plant them higher in the pot, meaning where the body and roots meet should be within half an inch of the rim of the pot. Again, not required, but I like them that way.
Another tip, if you live somewhere cold and wet you may consider putting it in an unglazed terra cotta pot. This helps it shed moisture. These soft-bodied Mammillaria are more prone to rotting than other species.