MONEY and JAIL (mostly)
21 for California.
no
In general, any felony makes you inelligible to own a handgun.
I don't know about California, but in most states there is no official gun registration. You can carry a handgun in California if you have a California handgun permit, but I understand those are hard to obtain in some counties.
You need to consult with a lawyer for a legally correct and current answer.
No.
You can read more on the California DUI penalties on the official California website for law enforcement. They provide you with the required information for DUIs.
What is concealment of information?
concealment of property
if a gun has a threaded barrel, (required for a silencer) it is classified as an "assault weapon" and is illegal in California.
FineImprisonmentDisqualification from OfficeRemoval from OfficeDeath
Strictly speaking, no. You can only buy handgun within your state of residence. However, you can pay for a handgun in another state, have the gun shipped to a dealer in your state, then go to that dealer to pick it up.