The SE's dynamics lead to decoherence, which makes MWI have branching. It's all just noticing the structure that's already in the system.
That's just regurgitating the teacher's password. MWI does not even account for the radioactive decay. In other words, if you find the Schrodinger's cat dead, how long has it been dead for?
Regurgitating the teacher's password is a matter of mental process, and you have nowhere near the required level of evidence to make that judgement here.
As for radioactive decay, I'm not clear what you require of MWI here. The un-decayed state has amplitude which gradually diminishes, leaking into other states. When you look in a cat box, you become entangled with it.
If the states resulting from death at different times are distinguishable, then you can go ahead and distinguish them, and there's your answer (or, if it could be done in principle but we're n...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.