Yes and no. They can't make retroactive alterations to the contract without your consent, but retroactive is more narrowly defined than you would perhaps like (

Yes and no. They can't make retroactive alterations to the contract without your consent, but retroactive is more narrowly defined than you would perhaps like (it would apply only to things you've sold, not new sales of games on old engines). Everything else on top of that requires deeper understanding of the contract law rules of the specific jurisdiction that applies and the very specific wordings of all relevant terms of service, and this is definitely an area of law where if you forget to execute the right magic steps, you can permanently foreclose opportunities for recourse. What opportunities you actually do have, I'm not sure--this is definitely an area where the answer is "talk to a lawyer", not get legal advice from randos on the internet.