For all screenshots, left is beta, right is final.
Bumpers and rings added to the starting point in the final
Ring placement, and this enemy isn't here in the final
The above enemy is here in the final
Extra life changed to bounce shield in the final
Item placement
The beta is missing balloons on many spike pits, or has less baloons to cover them, making some harder to cross.
Like here...
...and here
Here too
Again
...and again
I think you get the point.
Springs were added here in the final
Monitor swap