If you expose these to midday sun they tend to get a dull red color and don't grow as well, but they can tolerate it with enough water. Ideally, I give them morning and afternoon sun and try not to overwater them. The soil should be very well drained.
I haven't exposed them to freezing temperatures, just because they look kind of delicate.
It offshoots from underground runners and one will fill a pot over time. They grow fairly rapidly for a while with long spells of no growth in between, but that may be just because I baby them. This particular potfull was doing very well until I overwatered and they started dying like flies in a July window, so I'm more careful with them now.
Euphorbia decaryi flower in Spring
Euphorbia decaryi flower close-up