Qatar is an Islamic country but other religions are respected and Qatar’s cosmopolitan population supports many places of worship from Hindu temples to Christian churches. The timing of Islamic festivals and holidays depends on the lunar calendar, moving about eleven days earlier each year.
The attitude to dress in Qatar is quite relaxed, but visitors (men as well as women) should show respect for local culture and customs in public places by avoiding excessively revealing clothing in public places.
Context is important. Bikinis and beachwear are acceptable by the hotel pool but not in public places in the city such as shopping malls, restaurants and government offices.