see https://scratch.mit.edu/discuss/topic/370426/ press and hold space while clicking green flag will disable the dog cloning "cheat" (let go of space when you see variable 3 change to 1)
I've used a couple of "cheats", they aren't officially banned but they might not be in the spirit of the game! 1 - I clone the dog many times to stop the cats cloning 2 - I shrink the dog (I could have hidden it) also I've used (X position), (Y position) & (direction) to make "point in direction" and "distance to" blocks. The idea is to have the dog circle the centre at an optimum distance (which increases slightly as the difficulty increases), if a stray cat is found it gets herded in and circling resumes.