here is no limit as to amount earned. however, all money earned will be subject to tax when withdrawn from the RRSP. that includes the original $20,000 as this was deferred from your income when invested

NO there is no limit to earning potential

Is there a limit to how much money I can grow inside an RRSP?

For example, let's assume that one starts with an initial contribution of $20,000 and through a series of successful trades in the stock markets, they grow this initial investment along with other regular contributions to $1 million.

I need to understand if there is a limit, because hypothetically one could do regular contributions and be very smart in the stock market and make a lot of money (tax deferred) and build a great retirement nest egg.

I know that there is a limit to yearly contributions, but is there a limit to the funds that grow because of smart trading?