The forum seems to have gone to sleep, so I'll have a go at some of your plants.
#1 - not sure exactly. It looks like M. haageana but normally that doesn't divide dichotomously. However the spine colour doesn't look like M. parkinsonii, which usually is white-cream with darker tips. But still, I think parkinsoni is more likely than haageana. Has it flowered? that will tell you.
#2 is M. karwinskiana ssp. nejapensis, I think.
#3 - photo 1 of these 2 has M. spinosissima on the right, the darker straight spined plant. The two others in the pot are possibly forms of M. rekoi? yellow hooked spined.
#4 - I am not certain, but this looks like a form of M. bella (or M. nunezii ssp. bella).
#5 - I am certain, this is M. polythele, though not a typical one, but this species is very variable. The only thing I haven't seen before on this species is that the axils are not woolly, but appear to have short bristles.
I hope that others will add their views.