I know The OTG port is used to power the pi. So, how could I use a usb drive on that OTG port ? Could i plug a powered hub and the drive on the hub ? Moreover, is there any other way to power the pi while leaving the otg port to be used as a normal host usb port ?
Technically the USB ports of the Raspberry Pi are OTG (see USB on Pi). However the Micro-USB Type B connector I think you are refering to is simply for powering the device. Data lines are not connected anywhere there (refer to schematics).
As for the rest of the question I am actually not sure what's that about.