There are two "lines" of 10° latitude . . . 10° north latitude and 10° south latitude.
In Africa, the 'line' of 10° north latitude crosses Guinea, Ivory Coast, Burkina Faso,
Ghana, Togo, Benin, Nigeria, Cameroon, Chad, Central African Republic, Sudan,
Ethiopia, and Somalia.
The 'line' of 10° south latitude crosses Angola, Democratic Republic of the Congo,
Zambia, Malawi, and Tanzania.
(You can't get any closer to it than having it cross through.)
Chad
Guatemala
Cuba
the Bahamas
India
australia
No point on earth can have both a north and a south latitude, (except points on the equator, where latitude is zero).
What country having 15 degree - 30 degree South latitude, 45 degree - 60 degree East longitude
The equator is the 'zero' of latitude, so the smaller the latitude number is, the closer it is to the equator. There's no such thing as the 'closest' or smallest. You can name any latitude you want to, and no matter how small it is, I can always name a smaller one.
Indiana extends from (just south of) 38 degrees north to (just south of) 42 degrees north. The full degree latitude closest to the midpoint is 40 degrees north.
China
It is Brazil, South America.