> Do we run into the limits of undecidability?

For this particular canvas, no, as the canvas is finite.

Given enough time or space we can exhaust all states of the canvas and catch cycles. This applies to any finite canvas.

I would guess these are equivalent to regular languages because of the finite state. You can treat the different canvas states as states of a finite automaton. A finite automaton is a canvas turing machine by ignoring the canvas.