A student who has discontinued his/her education and must have an academic gap of atleast 3 years after his/her intermediate (12th) and Discontinued 1st and 2nd Year From UGC Recognise Universities can apply for one sitting examination.

Under Graduation in one year means that 3 years course will get completed in one year by giving all exams in one sitting only.

Yes, it is completely valid if you have valid Credits.

If a student has done 1st and 2nd year from a university then he/she can take direct admission in 3rd year which can be used as credit transfer.

Break in studies means Earlier you took admission in UGC Recognise Universities and Drop Out from the course.