phone codes/numbers in CA + USA

[Pflege]

Hello,

my question seems to be off-topic, but might be interesting for other
non-america resellers too. I am currently working on a script checking
the input of phone/fax numbers + ZIP codes wolrd-wide.

As I understand for 'normal' phone numbers in CA + USA exists only 1 unique format
(except for tollfree numbers / mobile numbers)
Area code = 3 digits
Phone or Fax: 7 digits

Is this correct?
Are there any other possible formats for phone / fax?

Concerning checking of the ZIP codes in the USA I noticed that
some users enter a ZIP code with leading state like
CA 12345
some are using the new format
12345-1234
and also
CA 12345-1234

Is the 9 digit ZIP code an official code and every city/locations does have
such a 9 digit code or are the 4 additional digits 'optional'.

Also is there an official rule concerning the leading 2-character state?

Thank you in advance

Matthias