Atm ive got some nafo tape player

gotta wait till saturday to wire up my pioneer one

(which defo does have a blue cable)
1. So it wont work at all without that connected to something?
2. I wont need a switch on the main power cable to turn the sub on and off (to stop the battery draining) as that cable does it for me when i turn on the head unit?
3. Could i wire it up to the power cable until i get my new head unit in?
sorry for all the questions im just trying to see what options i have atm
