Can I takeoff and land in Loiter mode?
With 3.2, yes. But I don’t do it often. It’s still safer to do it in Alt Hold. It would be too easy to have it tip over. You’ll notice I use a wide-set 3-legged tripod landing gear. This is much more stable and resistant to tipping over.
So in 3.1.5 I can takeoff and land in alt hold?
Yes, and sorry, that should have read you can do it with 3.1. Both Loiter and Alt-Hold.
The thing to be aware of is how it works, it will JUMP into the air the first foot or so, pretty sharply.
I don’t think I’ve ever done a Loiter take-off with a copter. That seems like a bad idea. Alt-Hold is better. Landing in Loiter is OK, as long as you’re ready to shut it down as soon as it touches! If you leave it on the ground in Loiter, it may try to tip over.