Hi Emma. I am with Jigs that I have not found any issues myself with combining different versions, but I’ll admit that I haven’t done that very much. I have heard though, that the practice is not recommended. I heard others state emphatically that doing this will eventually cause corruption. With that said I would be careful mixing and matching four different versions. That I haven’t seen before and would probably stay away, especially if the master project is updating its corresponding sub-projects of various versions. So I agree that “theoretically” that will work, but you’ll find recommendations on both sides of the issue.