It is possible to stay in Russia for a long period of time, if you have a business visa to Russia business visa to Russia (which can be issued not only for 3 months but for 1, 3 and even 5 years) and a second passport. You will need to leave the country every 90 days for a short period of time.
According to the Russia law, you can’t stay in Russia more than 90 days out of each 180. In order to get a lawful right to continuously stay in Russia for 1-3 years, you need to find an employer which will help you to issue a work visa with appropriate validity period.
This algorithm may differ depending on a country but the main points are:
- If you have a passport, you submit it along with a pack of necessary documents to obtain a business visa.
- After that you go to a passport service of your country and issue the second passport (you may specify as a reason that you need to obtain another visa while your current passport is used to apply for a visa).
- After you obtain a new passport, you submit it to a Russian Consulate to get a business visa to Russia.
As soon as you get both of your passports with visas, you may stay in Russia 90 days under the first passport and then 90 days under the second one leaving Russia for a couple days (or hours) using your first passport and then re-enter Russian under the another passport. Remember, you need to enter and leave Russian through different borders or different airports, for example using flights Moscow – Riga, St.Petersburg – Helsinki. Also you can go through any two checkpoints which are situated not far from each other.
Sure, formally you violate current legislation. In fact this violation is difficult to track because passport number is required to identify it but your passports are different.
You have a right to stay in Russia for 90 days under a business visa. After it expires you must leave the country and re-enter it using another passport with a visa under which you can stay for 90 days in Russia.
If you have questions ask them in comments. I will try to answer them all.