How many hour per day should I practice programming to be a pro?

Answer 1

I don't think time would apply, if you love programming then you will work without noticing how much hours, months or years you have put into it.

Answer 2

If you really do practice every day, even half hour will work. When you've practiced enough, you'll automatically know how much time you need to spend. If you want to have a routine, that's though quite impossible to maintain, because not all the problems are same, you'll just need to keep up the regularity.