One way is to read all of your state and federal firearm laws. Be prepared to read for a few days as there are a lot of them.
A better way is to talk with a lawyer who specializes in firearm law. I would recommend against asking the police because most of them know very little if any firearm law, and some of them make it up as they go.
The things that are most likely to keep you from being able to own a firearm "legally" are a criminal record, drug abuse, and restraining orders.
As a rule of thumb, if you have a felony conviction, you may not posses either firearms or ammunition. If you have ANY felony conviction and are within close proximity to a gun, you can be charged with Felony Firearms, and potentially face ten years imprisonment for the gun, and ten years each for the rounds.
First, look up the federal list of people who cannot possess a firearm. Note that there are a couple kinds of people who cannot "buy" a firearm, but they could possess one (e.g. people under indictment for a felony but not yet convicted, who already owned firearms before the indictment).
Then look up your own state's laws on the subject to see if they have any additional restrictions on who can buy or possess firearms, or ammunition.
If you don't get a definite answer just by looking at the federal and state lists and remembering your own history, then the next step is to see a lawyer.
Search your state gun laws or call a gun shop. I know here in ÇA you need to be 21 for a handgun and 18 for a long gun. Your state maybe different.
You can't.
The question refers to a California petty theft statute - If that statue is NOT a felony offense, then yes, you may own or possess a firearm.
Based solely on the information provided in the question, NO, they may not legally own or possess a firearm.
Legally, yes. A firearm is defined as the receiver (frame) Even when it has been taken apart, the receiver is still legally a firearm.
Yes, provided the firearm itself is legally obtained.
You will need a lawyer and money to find out the answer.
Very severe restrictions on possession of any firearm except by members of the government/ military.
You will need to consult with a lawyer for a legally correct and current answer.
Assuming this is a firearm you own, you can sell it to a gun shop, give it to a friend in your state that is an adult and able to own firearms or contact your local law enforcement officials and surrender the gun to them.
Be of legal age and not be legally disqualified from purchasing a firearm.
A felon is no longer allowed to legally carry a firearm.
As many as you'd like, so long as you can legally own a firearm. California attempted to enact an "arsenal license" in 1994, but it was struck down.