Hello,
Regarding device hardware revisions, the only thing you should be looking after, when considering firmware updates to the current RutOS, is your device's product code. If the code contains RUT950 *G1***, you will not be able to perform updates to RUT9_R_00.07.00 and above, otherwise, you are advised to update to the latest available firmware for variuos fixes and security updates.
Both RUT950 and RUT951 are supported. The only difference between the two being in the CPU used. In term of functionality, the devices are identical.
Best regards,
Žygimantas