There are no February preptests available because the February exams are not disclosed. Meaning that the February exams are the only ones which LSAC does not release. Even for those who take their exam in February, they can only see the answer choices they got wrong but can't see the exam they took. I think LSAC has historically released a few of the older February LSATs and you can get three of them if you purchase their "Official LSAT Superprep" book. That book contains 3 LSAT exams from February 2000, 1999, and 1996. However, with all the tests available perhaps purchase this if you run out of tests or you need additional tests to drill with.
They are not any harder or easier than any other test. LSAC just keeps tests undisclosed in case they need material for make up tests and international versions.
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The link is below
http://www.amazon.com/The-Official-LSAT-SuperPrep-Champion/dp/0979305063