I had forgotten my NETGEAR extender loginpassword, what can I do in such scenario? Is there any other way out other than to go for factory reset?

NETGEAR extender login password and username are must in case you want to alter or modify any configuration of your extender. In case you had not changed extender login password and username then their default entry will be:

Username: admin
Password: password

By entering these credentials, you will be able to login into setup page.
But in case you had changed username and password for your NETGEAR Wi-Fi range extender then these default entries will not work and you need to enter these changed entries to get logged in.
In case if you had forgotten these credentials then best possible way is just to put your NETEGEAR wireless range extender on factory reset and launch new extender setup again.