It's difficult to trace the company/reseller as the router has been sold through ebay/Amazon. Surely, the whole point of firmware reset using .rst file is to upload fresh config copy with default password as well. If i can't get into this router, this is a brick to me. There must be a way around it; not prepared to accept the defeat yet.

. Surely, the whole point of firmware reset using .rst file is to upload fresh config copy with default password as well.

That's correct... but you still have to know that default password. This may NOT be the case with your router, but some companies buy special versions of the products with their own custom config or firmware. The router normally remains their property so it's not yours anyway and whoever sold it through ebay shouldn't have - like a cable TV or Sky Q box. However, if that's not the case with yours, the reset just isn't working or you're doing it wrongly.