For every session GARP releases practice paper for FRM candidates to give an insight of actual exam. GARP FRM practice paper consists of 100 questions for FRM Part 1 and 80 questions for Part II. These practice papers are really important from the perspective of knowing exam type questions and difficulty level of the exam. These practice papers will help you understand, what to expect from the real exam.
Due to a new set of practice papers for every session, students try to collect previous practice papers (Like past 10 years practice papers) in order to get more number of questions to practice and get a better idea of the exam. The catch here is, all practice papers (previous and current) have the same questions. If you see any difference in the previous question set, the reason is GARP deleted some question from the previous practice papers in order to update practice papers according to current curriculum. Rest is the same. So solving multiple practice papers will not add any value in your exam preparation.
So the answer to the above question is, solve a single GARP practice paper and it should be that applicable to the current session.