The backup application is pre installed. It's called "Backup" and the icon looks like a safe

Is multitouch possible on N900. Is it a hardware limitation or software limitation?
Is there any application like task scheduler which can even send sms on a specific time?
In how much more time good 3D games will be available for N900 like NFS Shift, Fifa 10, etc.?

IS there any place where we can ask questions?

Forgive me for answering only your first question.. I'm not sure about the second one (I heard there is) and really anxious to know the answer to the 3rd

Regarding multitouch - the touch screen for the n900 is resistive, which can respond only to a touch on one place of the screen at the same time.
In oppose to captative - which can "understand" more than one spot of preassure, but also less accurate (e.g. you can't use stylus).

there are some experiments to check multitouch "immitations" using software workarounds, but nothing has reached final development stage and it doesn't look like it's going to be implemented in the OS itself (Maemo 6 with n920 suppose to be multitouch - so I've heard).