I am using RB1100. If i go into logs, i could see log entries upto only 3rd Oct, is there any way that i could see log entries older than that???

By default you can see only 100 log entries. Older ones are deleted.
There are several options:
*) write logs to file
*) increase log limit

Or send the logs to a remote syslog, which is handy if you have several routers and you want to see all the logs in a central place. (although any log entries sent if/while the remote syslog is unreachable will be lost).