ANSWER:

The most correct opinion is that qunoot should be read after ruku.
Yes, qunoot is not mandatory, therefore if you don’t pray it all together then also your witr is valid. 

I read qunoot before going to ruku as I was told you can read it before or after ruku and both are valid. Is this correct? Also i was told that qunoot isn’t a must for Witr so you shouldn’t make it a habit to say it all the time. Every now and then is better. Is this also correct? Jazakallahu Khair. I pray your Ramadhan is going well and please remember us in your duas.