Generally, objections to your discovery responses do not help your case. You want answers. You have to "meet and confer" with the plaintiff to discuss which answers it should supplement. If you do not get satisfaction informally, then you can take it to court.
That the plaintiff bought your debt is just irrelevant. True, it probably bought it for pennies on the dollar, but that fact has nothing to do with its right to enforce the debt.
It would help your case if you didn't owe the debt. Otherwise, and as it's clear you're out of your element, you're most likely just wasting effort and should probably try to resolve the matter through settlement.
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