Answering a "Plaintiff’s First Demand for Interrogatories To Defendant

A few weeks ago we were in court with a collection agency. My defense was the account was never validated. Judge told the lawyer to provide us with proper documentation and scheduled us to come back in November of this year, 6 months away. Received a letter yesterday from their lawyer. With the letter came two copies of “Plaintiff’s First Demand for Interrogatories To Defendant”.

-I am supposed to answer “I have no sufficient documentation to agree or disagree” to each question, correct?
-Do I have to get these papers notarized?
-What do I do with the two copies? Is one copy for the lawyer and one for me? Or do I have to file it with the court somehow before our next date? Or just bring it to court at our next appearance?

Also with the letter came copies of “Bill of Sales”. None of them are on any sort of letterhead. They do not list my name, account number, social #, amount, or anything that identifies this is me or my account that is being sold. The travel of this account went:

From original CC to Collector #1 in 4/2007, to Collector #2 on 6/1/2007, to Collector # 3 on 6/6/2007, to Collector # 4 on 6/6/2007 (same day it went from #2 to #3!), to Collector # 5 on 7/25/2008.

The only collector I ever heard from was collector # 4; which a DV was sent but response never received. I have documentation proving this. Then it went to collector # 5, no contact was made from them until I was served for court.

It 2008 I made three written attempts to the original CC (again, I have documentation) asking for documentation from the account (statements and such) but did not receive reply.

The last piece of documents received was an excel spreadsheet that has an account number, my husband’s name, SS#, address, & phone number. Then there’s a charge off date (3/2006), last payment amount, last payment date (12/2005), original client name, open date, current balance (which is 50% less than I am being sued for), and the seller name which is Collector #4…not collector #5 who is suing me.

It seems to me that this described excel spreadsheet, which is not on any sort of letterhead, belongs with the bill of sale from collector #4 to collector #5 (who is suing).
-Is this sufficient proof of validation? Or, can I request copy of the contract, last statement, payment history, explanation on how they calculated the amount they are asking for, etc?
-If I am allowed to ask for the above documents, do I just put it in a letter and send it to the law firm? Do I have to send/file a copy with the court, or do we do that on our court date?

Or do I not request additional documents, and wait until I get to court and then motion to dismiss based on no proof of debt?

Thanks for the help! This is my first time going through court.