1. If the change in rating can be done at the discretion of the management then nothing could be done. However if the ratings once fixed become beyond the control of any party then it's case of 420 ipc.
2. FOr this you have to lodge complaint with police for tampering of official data.
3. You can lodge complaint with your current location unless the tampering can only be done from Delhi.
4. Criminal case attains importance only if complaint is lodged at the first possible opportunity. So do the needful at the earliest.