My quick answers to your questions:
  1. Not really necessary. All depends in what status are you going to respond.
  2. Depends if are included accusations. Then you send back a letter with more questions to be answered, as Lux said "conditional acceptance". That is very important. You put some questions about those claims that they cannot rebut. If they cannot rebut, then their claims are null.
  3. Read https://livingintheprivate.blogspot.com/ and you will learn how to sign or autograph.
  4. You can use https://opentimestamps.org/ as "online notary", with the document signed also by 2-3 witnesses. But again depends on the gravity of the claims. If is just a speeding ticket you don't have to bother too much, not even open the letter, stamp it with those "no contract" stamps I've sent you and is done.
  5. Yes be prepared to send more answers and prepare your UCC status.