probably you must be a russian in order to register it, because it is same on almost every country code top level domains
yea a few geo tlds require you to be an actual citizen or passport holder of the country to get it. Others are public, I believe .ru are public and you can register them from an ICANN accredited dealer that has clearance for them - they may be a bit more expensive tho.
yea, it's very hard to register .ru domain even for Russian citizens. Situation has become better in past 2 years, before that you were required to sign registration documents personally. As for now, you need to provide your passport details (and ofter a scan of your passport), you also can't transfer your domain to other registrar or change ownership without providing your passport copy. However I've registered one of my .ru domain without any paper work at www.tuthost.com (Ukrainian company), that also accepts PayPal. For people, who want to get a .ru domain (with a little knowledge of Russian), I recommend this registrar. It takes around a week to register this domain, so you must be patient as well