I have kept cacti off and on for most of my married life (almost 50 years!) but have usually only had two or three at a time and never really knew what they were. I am trying to get into it again and am more serious about doing it properly and knowing the names.

I am pretty confident that the first one is Mammillaria. But the species?

Is the second one with the "twins" also Mammillaria? Can you narrow it down to more specific?

Is the last one shown below Parodia? Don't know the species. Maybe magnifica?

None of these were labelled at the hardware store; I am just trying to match them by a few pics in a book. I won't feel too ashamed if you have to correct me!