Yes, there are a variety of websites that offer samples of the California DMV written test. There are five sample written tests on the DMV website for the State of California. Search under publications to find the tests. The tests can be taken numerous times. These should give you enough practice to pass the test.
Only an unofficial one. You can retake the written test a week after taking it, just try try try try again! You can go to the local dmv and request a brochure that will tell you everything you need to know for the first. The test is very very easy and covers the basics.
Yes, you can. There are textbooks, online tests, and other resources to help you prepare for the written test, which is mostly multiple choice anyway. Thusly, you can practice without it actually counting.