I believe I made a mistake when adding my tuition expenses for the years 2020 and 2021, can I submit this to CRA? Am I still entitled to get that credit?

Unfortunately,  you will need to make adjustments on your 2020 and 2021 tax returns. Per the CRA, You can request a change to your tax return by amending specific line(s) of your return. 

We can certainly help you make adjustment to your previous tax returns already submitted. Please read this great TurboTax guide to learn how.

Thank you for choosing TurboTax.