What is the difference between A+ and ARH+ blood group?
Nothing--they are the same. "A+" (A positive) refers to blood that has antibodies for both factor "A" AND for the Rh factor. The word "positive" means that there ARE Rh factor antibodies present on each blood cell, so "A positive" actually means "Rh positive."
If you belong to the blood group A, you have A antigens on the surface of your red blood cells and B antibodies in your blood plasma. A person with Rh- blood does not have Rh antibodies in the blood plasma. However a person with Rh- blood can develop Rh antibodies if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies.
With that in mind, ARH+ blood is one that has recieved the antibody from the Rh+ donor.