manojkumaru, I see the proposed solution as the best:

3. They have been trying since 4th oct and couldn't fix my usb hub back onto the board. Also, they tried to swap the board with an Old n900 board, whose IMEI found to be from England and is more than 2 years old already. I didn't want such an unprofessional replacement. So turned it down and escalated the problem. Asked for a new N900. But they don't find one in India they say.

This is really better service than many of us N900 users may expect anywhere in the world.

If they can replace the motherboard without filling the phone internals with sand and crumbs, I'd opt for this especially if "they" are Nokia and extend your warranty after repair.

In any case try not to be too much of a modern consumer...IOW, be careful that the warranty claim does not work contra-productive and makes you end up without N900 and a dumbphone you will want to sell at half its market price.