there is no estimate for the number of scholarships, it depends on the donor country. I've told you an estimate of Chinese govt scholarships in the said program, the donor countries other than China give a small number of scholarships which may range from 5 to 10, not more than that.
Regarding the test you can't opt for social science as you are a business graduate, but after the test if you are able to qualify the test then you can choose your field for masters, which may be different than your department.