Ok...I'm far from being an expert on this code lark as opinions sometimes differ an my memory plays tricks but here goes.....
I think the chip is "read only" which means once it's coded that's it, the items you mention may have a "re-writable" memory? I do know the ECU can have it's "code" erased but then you are left without the protection for your car.
Therefore your second hand keys won't work as they have already had the code, from whatever car they came with, burnt into them. They Master key has the all important info that is need to install and code a new set of keys, losing that will render your system useless in the event of failure.
As for failures I've no idea. It doea appear that the Alfa code system is a bit fikkle and likes to challenge us occassionally!! Sometimes a failing battery is at fault, sometimes a fuse of sometimes simply that the memory is lost, no idea why!
Not much practical help but hopefully, if this is accurate, some understanding?
...as for the replies, don't worry, it's alwasy a bit quiet around here at the weekends