For your proposed modifications, from your description 1 and 2 would not count as significant modifications on their own. 3 would, keep in mind that your 1 and 2 would be a part of making unique levels and each unique level you create can count as a significant modification. When you submit your final project be sure to change your modification description to be more descriptive of how each level you have made is unique from the others so you can potentially earn full points.