the only way to depend on DE's sol is to either argue PA does not have jurisdiction for some reason or that PA must abide by DE's sol for some reason. I have a horrible time accessing any PA statutes so I cannot help much there.

Them selling the debt is not the problem. You moving is the problem.

curious as to how you know the exact date of delinquency of this debt. What are you basing that on?

by chance, do you have access to a copy of the contract? If so, you might want to check to see if the contract states some particular states laws apply in actions concerning the contract.