Legal Question in Civil Litigation in California

There are time limits for serving and filing a proof of service. They vary by court. The penalty for not complying, though, is generally a scolding by the judge, as long as you get them served before the first Case Management Conference.

Yes there is a right to one amendment before service, or even after service as long as no defendant has filed a response. Even once a response is filed, leave to amend is so liberally granted that no defendant in their right mind refuses to stipulate to the amendment, unless there is a flaw in the complaint that is so fatal it could end the case, such as if a cause of action was left out and the statute of limitations ran out between the filing the first complaint and the request for a stipulation to amend.