Does buying a new stove for the rental property to replace a broken one count as repairs or CCA?

Usually you would take CCA on items such as large appliances. You can use Class 8 with a CCA rate of 20%.

I have the same issue except I never claimed CCA for my old appliances over the last 3 years of owning the rental. So what do I do about that?

If you have just bought a new appliance, then you can enter it as a new class 8 asset in the CCA section. You can also enter your old appliances as well, but you would need to figure out their current value, rather than putting in the original price you paid for them.