Smart Contract Revoke Question

First off, I am new to crypto, so go easy on me please. My question is about smart contracts, revoking them and by doing so, what does that mean.

I entered into a smart contract with a DeFi app for Ether mining. Apparently, when I entered that contract, they automatically withdrew my Eth and locked me into an insane requirement. I contacted their support and they informed me that I have to meet the requirement of the smart contract in order to withdraw my funds back into my wallet. The requirement is that I deposit an additional $20,000 worth of Eth at least into the smart contract in order to fulfill the contract requirement and be able to begin a withdraw or else my funds will be locked in the contract forever.

Is this standard practice for a smart contract?

If I revoke the smart contract, will my funds be automatically returned to my wallet that they initially took from me?

The Dapp is called Defi-Ethermine. Anyone have any experience with them?

Thank you!