starbucks & dunkin donuts on lock screen

a) I have my Starbucks and Dunkin Donut apps (passes ?) displayed in my Wallet, I can see then when I open Wallet.

b) Why don't I see those two when I double click the Home button ? All I see then is Apple Pay and Airlines. Should I be able to double-click the Home button, and access my Dunkin Donuts barcode from the Lock Screen ???

separate question:

a) In the Starbucks app, it says "Apple Pay Enabled", and shows it as a form of payment along with my credit card.

b) What does that mean ? How/when do I use Apple Pay to pay thru the Starbucks app (mobile ordering for instance)