ChibitronicsWhite LED Circuit Stickers - Megapack, 30 white LED circuit stickers

Is there an on off switch to use with this? I could see the battery exhausting rapidly if you put it in a card with no shut off.

If i wanted to light up 60-90leds (entire white classroom pack in a single project) , what sort of psu would be required?

Once it is stuck is it permanently stuck or is it reusable?

How many leds can you light up at a time with one battery?