When is the best to release the product on Product Hunt? I have never seen the product like MVP there. All of the products are high quality.

I think it's up to you as the maker. Like anything creative, you as the creator makes the call of when you think it's ready to show to people. I say find the balance between perfectionism and impatience (of seeing the fruit of labor) - release when YOU feel ready. People naturally want something polished and bugless, so that's why eventhough there're lots of MVP on PH but you don't see them right away because they weren't been upvoted.

Amie Chen