Legal Question in Credit and Debt Law in California

Yes. Four years is the legal time limit.

Yes... and while technically you could defend yourself successfully by claiming the defense of the statute of limitations after 4 years, that does not mean you may not be sued after 4 years or that the debt will disappear from your credit report after 4 years. The 4-year statute of limitations is an affirmative defense. This means that if you are sued more than 4 years after you defaulted on the debt then you must still answer the lawsuit in writing, pay the court fee to file the answer and allege in the answer that it has been over 4 years since you breached the contract to pay the debt. There are exceptions to the statute of limitations although rare ones that may allow a creditor to sue more than 4 years after you stopped paying without the consent of the creditor (defaulted).