If I had lived half my life in Pakistan say from 0 to 20 years, and then moved to UAE and live here permanently, would it still be qasr if I go back there for less than 10 days?

It depends on your intention when you left Pakistan. If you left it with the intention that it’s still your Watan, then you pray their full even if staying there less than 10 days. If you left with the intention of it not being your Watan, and not intending to go back and live there, then you pray there Qasr.