Just coming in on the yoga stuff, I've continued a dedicated practise for a few years now. I wouldn't say I'm an expert or really a yogi but i've spent quite a chunk of time doing it and reading about it and attending classes/workshops.
I would agree with what was said before about it being about progression and to be honest I think the handstand looks pretty good. But yoga isn't about achieving each asana perfectly. Some asanas are not able to be performed by many people, some take time to build up the strength for and some you just have to get wrong about a thousand times before you get it right. And even then! you can't necessarily bank on that asana being a regular part of your practise. Each time you step onto the mat is a new day. Somedays I step onto my mat and I can already tell that despite touching my toes no trouble every other day, that day my hamstrings are stiffer and I must work within the limits that my physical body has given me with each practise. And I think that word practise is really key here. It's a yoga practise not a yoga perfection.
A note on the sucked in stomach. Obviously it may well just be posturing for the 'gram trying to look thin and highlight her body.. but it could also be that she is trying to utilise Bandhas or "locks" in her practise. There's the Mula Bandha which is the pelvic floor, the Uddiyana Bandha which is at the navel area and then there's the throat lock I forget the name of that one though.
She could be trying to engage the Uddiyana Bandha hence the sucked in stomach but I should say that you're not meant to completely suck in your stomach or you'll affect the breathing which is the key for helping the prana circulate.
Anyway probably not too interesting but thought I'd chip in.