I'm trying make an IoT device which I want be a highly power saving one & want it to work in a remote static environment. So I plan to make a circuit with a "SARA" NB IoT module. Now I want to know if FOTA is possible with NB_IOT.
Yes, explicitly so, albeit it will be relatively slow.
Carriers are actually recommending NB-IoT and Cat-M1 combo modules, and dynamically switching to M1 when FOTA is needed, although this will only make sense for some apps.