The Germans used their 20mm in an anti infantry role, I am trying to remember seeing it used for executions, forget, could be in a film rather than historical. Could be USSR
I have seen some people who apparently apply again and get it, quite how often this happens I have no idea, I doubt it is that common but they only have the application fee at risk.
I remember entering the US and was asked how much I had on me, less than $20 in USD but like everyone else I had CCs.
Begs the question how many people visiting the US do not have Bank Accounts, must be very few.