planning to visit hk for 3 months

If you want to apply for a tourist entry permit for HK, you need to provide copy of your passport, the application form, a bareheaded color photo, hotel reservation, flight itinerary, proof of your financial support, and your travel plan. However, I cannot assure if you can get 3-month stay duration because the consular officers will give you proper one based on your travel itinerary.
If you submit your application to the embassy of PRC and it is processed, it will cost 1600 pesos; but if your application is transferred to HK immigration department, you need to pay extra commission fee 1350 pesos.
If you post your application to HK immigration department directly, it will cost HKD 190.