Clinical Psychology

Most common stream that candidates engage with to pursue psychology at undergraduate level is Arts (Humanities) stream because most Arts (Humanities) programs have Psychology in curriculum. Also Arts (Humanities) stream offers students privilege of recuperating into theories and ideas associated with mental health. 

Science and Commerce students can also apply to Clinical Psychology courses. It's just a matter of interest in human behavior and willingness to learn about and help human mental wellness.

General Psychology includes aspects of human behavior, cognition and emotional development. You will find different branches like developmental, social and organizational psychology under this umbrella.
If you look at Clinical Psychology it is all about mental health, psychological disorders, assessments and therapies. It prepares you to work in clinical or therapeutic settings and help people manage their mental and emotional issues.

Yes a number of universities in India accept students from any stream into undergraduate Clinical Psychology courses, regardless of whether they studied Psychology in Class 12 or not. Yes, prior study of Psychology does give you some background in subject.

Some top colleges may prefer students with a psychology background, however, majority of UG courses are written with intention that they will be teaching students who have no previous experience studying psychology.