Can I get 4 hour transit visa in hongkong airport?

Ravi, if you want to make transit in HK, you should apply for a transit type entry permit in advance, rather than get it from the airport. You can apply for it from the PRC embassy in the country where you are or from the HK Immigration Department directly by posts. The application documents include a photocopy of your passport, an application form, a bare-headed photo taken within six months, transportation tickets, and a financial standing proof.