I got a summons for debt I dont owe

If its a real summons, yo must file an answer. Get a lawyer or you will end up potentially owing more.

Should I hire an attorney for "failure to ID" ticket?

Then yes you should. Changing to criminal defense

I have a notice from a collection agency for an invalid debt (for a debt already paid in full), will it affect my credit report?

Ask for validation and provide proof of payment.

Do I have a case?

You should consult with a local personal injury attorney, facts are missing.

I had a procedure done a few weeks ago for my spine.

Your going to need an experienced PI layer to help you. You will need your medical records. Consultations should be free but be advised med mal...

Anyone can be sued for anything. But, there is a qualified privilege to make a report to the State Bar about your attorney. Truth is a defense to...

The worst scenario if you fail to answer. File an answer and talk to them. See the other answer also.

Is discovery ever entered into evidence in debt collection lawsuit

you need to file a motion to compel, I agree. You also need the court to rule on the objections. You really need a lawyer.

Is it legal for me to write the received date on someone's check to me? Front or back of the check?

The memo section, lower left. Also, copy envelope, and check and send a traceable letter to them telling this is late and your acceptance does not...

Collection debt

It means they sent the plaintiff discovery admissions which were not admitted or answered and they became deemed admitted by operation of law. The...