Tip: When making your overworld, mix the terrain up! Add decorations to the overworld. Don't leave large empty grass or sea regions. As an example, angled land and multiple colors look much more interesting than square land and flat, plain colors.
If you stand on that block you can't jump but you can spin jump.
No credits nedded.
There's a few issues with this block. First off, you absolutely don't need to repeat the same code 6 times for the 6 labels you use it in, you can just have it once and put all the labels you need right before it. Second, most of these labels are unnecessary: if you want to make it work when Mario is standing on it, then you just need MarioAbove. A consequence of this is that jumping is disabled also when touching the block from the sides, which I assume it's unintended.
Finally, I think this is too specific for a submission, and besides that it can be already achieved with this block.