how long will it take to recive HK tourist visa? what are the requirments and the cost in total?

Henok, you may try to ask the embassy whether they can issue visas for HK by calling 00251-11-3711960 or 00251-922-726200. If they can't, you need to apply from HK Immigration Department directly by post. It takes four to six weeks. The total cost is around HKD$340.

You need to provide: copies of your passport information page, filled ID1003A form, a recent passport photo, personal financial statement, flight tickets and travel itinerary.