Quixote

If the plant is endangered, don't take anything from it. If you don't know if it's endangered, it's endangered.

Scop/Pach hybrid, I'd say. Too light green and the spines are a bit too prominent to be pure scopulicola, in my humble opinion. The colour could be a trick of the flash and camera though. Try taking a pic in natural sunlight.

Why stop there? I want a loph fruit smoothie...

Don't bother with sulphur dust. Just let the cut dry thoroughly before sticking the cut end into the soil. Thoroughly means at least 2 weeks, preferably a month at room temperature.

It seems especially strange that your cactus has made a pup immediately on top of another small pup. I've never seen them pup from the tip without the tip somehow being damaged. Maybe there's some bug or snail or infection that has damaged all the tips at once?

When cacti call out to you, you are well on your way to achieve true cactus-consciousness.

Looks like a severely dehydrated Pedro. Is it soft to the touch?

Which species ? Looking at Wikipedia, there are many, and they seem very different. https://en.wikipedia.org/wiki/Turbinicarpus#Species_list

Rebutia looks like a good candidate - to me it looks short and fat in the picture on wikipedia at least. https://en.wikipedia.org/wiki/Rebutia Also of course Lophophora. I have one that gets older and more beautiful year by year. Never get bored of that

Looks like a nice little cactus, but I was hoping to find one that flowers once in a while throughout the year. I guess such a cactus just doesn't exist, as in their natural habitat there's only one time of year suitable for flowering...

Thanks for the suggestion. Was hoping to find a cactus that would be happy inside though, since the climate in Northern Europe is pretty dismal for at least 6 months a year..

I'm looking for a short, fat cactus that has big and frequent flowers. Any ideas about what to go for? Ideally one that would flower all year round when living indoors in a pot in a window. But I guess there are no cacti like that.

How come you don't like them?

Call She-hulk

When it comes to pots, bigger is better, I think. So it's mostly up to you how big pots you can practically handle. The cactus will happily fill any pot you care to give it. And don't believe the stuff you read about gradually replanting into bigger and bigger pots. My experience is that roots quite quickly fill all the available space. There's no downside to having the unused soil sitting empty before the roots reach it. As long as the pot is free draining in the bottom and has plenty of pebbles and coarse sand mixed in, the plant won't get waterlogged.