You mentioned the circular room; perhaps the doors they show in the shot when Jefferson and Regina enter that room before going into Wonderland are only just some of the doors. There may just be other doors that are there and we cannot see because they aren’t shown.
That’s true. There are 20 doors, but we were only able to see 16 of them. 😐
Plus…even though some of those doors are obvious like the Oz door, the Oriental door etc…..there are some that may not be so clear. Then those 4 mystery doors will bring out much curiosity in us all.