Can $220 airport express travel pass use with tram, bus and stores accepting octopus card in HK?

I bought $220 airport express travel pass and already used for HKIA to city. Excluding refund of $50, i will be left with $70. Since it is the octopus card, can i use it with other purchases besides mtr such as from 7-11? Can I use with tram? bus? is it true that it has $20 store value? Or do I have to top up some cash in it for taking bus?