When you arrive in Russia you will not be required to stay in the hotel that issued your voucher. You will however need to register your Russian visa at a hotel, police station or post office within 72 hours of arrival.
Russian police are known to stop travelers at train station and in the street to check their legal status within the Country. If you do not register your visa the police may fine you up to $100.00 US dollars and you could be deported. If you are deported you will not be allowed back in Russia for at least 5 years.
Please check out the lnk below for the Russian consulate's FAQ page.