Legal Question in Criminal Law in California

No, unless you are law enforcement, and there are other limited exceptions such as to records a threat of violence, etc. Otherwise it is illegal, however rarely are crimes charged for it.

It is usually illegal. There are exceptions, so you may want to review the details of your situation with a lawyer.

It is illegal, unless they are law enforcement with a wire tap approval or a person who has been obtained a protective order and obtained permission from a judge to record your conversations.

There is at least one other exception that Mr. Marman and Mr. Roach haven't mentioned. Recording someone can be (but isn't necessarily) legal if he cannot reasonably expect his remarks to be private. This doesn't happen often. But if, say, you record someone who is yelling at you on a crowded street corner, you probably are not breaking the law.