Is it correct that if you don't use leverage you will not be liquidated no matter how much a cryptocurrency falls?

This is correct.

Since the initial principal investment was your money and not the broker's, you do not need to be concerned about being liquidated when the price of a cryptocurrency falls.

If the broker or exchange trims your investment for liquidation reasons, you might have fallen victim to a scam. For the most part, if you are using an established trading platform for your crypto needs, you do not need to be worried about these scams.