Existing firewall is 1/2 inch adding 1/4 sheetrock to make thicker(1 hour rate). Can I use liquid nails and 1 1/4 screws together or screws only(how long). Can I mud from ceiling to floor or use fireproof caulk on seams. The wall is in strip mall.

The city codes will lay this out. You must have a permit and know which code you town follows.

Since it is a commercial application you should have obtained a permit. What do the code people say? To be a true rated wall, it must have X rated drywall. Some locals will allow a regular 5/8 build up like you are proposing, some won't.

GAboy, I can't answer since you do not say where you live or which codes must be followed in your town. So does this post then mean you are doing work off the books and without permit and still think you are a pro but can't do it without our help.