I really don't undertand people and this question.
How stable can alpha software be. If it was a stable software don't you think they would release it.
if you cannot deal with bugs and crashes and freezes and things not working as they are supposed to do not install any TP software on your phone.
This build, and the one after it will not be STABLE. it will just be better than the previous.
I'd say a hard reset isn't needed if upgrading from 8.1. I'm not sure if that is the case if upgrading from a prior tp.
How about basic things like receiving-sending text messages and calls? in the current build
These things work fineOf course in 10136 you couldn't spend a lot of time in messaging apps, because it would crash, but I haven't been that busy with messaging so far, so I don't know. Calls work just fine for me
I have a hard time telling I'm not in the 8.1 messaging app now. It works good.
FYI. On my L520 spare phone the SDCard disappears once in a while and I can only get it back by soft reset, sometimes multiple times. Did you check whether the SDCard is showing up under Storage?I have a problem with the SD card in 10149 on Lumia 535.