FYI, those sound like credit check questions. They probably did some sort of credit pull.
(They know the answers to these because the credit reporting agencies know how much the house cost, where it was located, what previous address(es) you've had on your credit accounts (including credit cards), etc.)
SSN data isn't flawless. My brother and I somehow had the same SSN until I was in my teens (right as I started working but before he did so thankfully it wasn't too difficult to fix).
Doesn't matter. The credit bureaus mix people up all of the time, particularly if you shared a name and street in the past.
My wife and mother in law share a first name. And a middle name that varies by one letter. (Ie. Mary Ann and Mary Beth) credit reports routinely mix them up.
When I was in school in 1996, a collector managed to get a business debt of my grandfather (who shared a name and died in 1986) attached to me.
(They know the answers to these because the credit reporting agencies know how much the house cost, where it was located, what previous address(es) you've had on your credit accounts (including credit cards), etc.)