what rules/codes govern an amended demurrer in a unlimited civil suit?

I've never even heard of an "amended demurrer." If the "amended demurrer" is not timely, then I would oppose on that ground.

Hire a lawyer. You've posted a large number of questions on Avvo in the past month, and you must realize that you can't litigate a case this way. There are literally hundreds of thousands of lawyers in Southern California who specialize in landlord/tenant litigation - hrie one.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.

Ms. Koslyn is right about trying to use Avvo in lieu of an attorney.

Your rights could be irrreperably prejudiced by not being represented by able counsel.

In answer to your question, there is no pleading known as an "amended demurrer" I am aware of.

If the subsatnce of the demurrer was changed, and you did not get the requisite 16 court days notice, you could object on that basis.

If you got the requisite notice, the judge could hear the amended demurrer as you were not prejudiced by this this unorthodox pleading.

Moreover, the defendant can raise the same issues in a motion for judgment on the pleadings that can be brought after an answer is filed.

I would strongly urge you to consult immediately with a litigator skilled in this area of the law.

PLEASE NOTE THAT THIS RESPONSE SHOULD NOT BE CONSTRUED AS A LEGAL OPINION OR ADVISE, AND DOES NOT CREATE AN ATTORNEY-CLIENT RELATIONSHIP. IN ORDER TO RENDER A LEGAL OPINION OR ADVISE, THE RESPONDING ATTORNEY WOULD NEED FAR MORE INFORMATION THAN HAS BEEN PROVIDED, AND WOULD NEED TO BE RETAINED PURSUANT TO A WRITTEN FEE AGREEMENT.