OK, I did clear the device. and everything is fine, ubiboot still works and harmattan aslo boots up. All partitions are also OK. No problem (yet).

I guess clearing the device just clears the home partition and leave rootfs untouched (removes all the installed apps though)

Because i had added the repomirror list manually, it is still there. i am able to enable developer mode(there is an exclamation mark beside the switch, don't remember if it was always there), also the ubiboot config files were in there. they are also fine.

How does this removal of apps happen? where is the information about the user installed packages stored (i don't know how apt works)?
And is it possible to edit it manually to have some important apps preinstalled? like terminal filecase etc. What information should i add there?
Also what all packages does terminal require? I want to have developer mode enabled by default.

EDIT: Nothing was cleared, i still have my old accounts, old app settings, contacts, call logs, photos, everything. also root's command history is available. all it did was uninstall apps. I guess it tried to look for old partitions didn't find them so didn't do anything. But how does it look for these partitions? if it is by partition number then root should have been gone.
Can we get the script or anything which is responsible for resetting and clearing the device? or is it integrated into settings?