Not 100%, but in my experience..
>What CAN & CAN'T be plugged in? And when?
I use a mic/earphone combination, the same one as on a mobile phone(PHS here
in Japan) I plugged and unplugged it numerous time, while the machines was
in different states, NO problem yet.
>What exactly is the difference between the jack in the front & the jack in
None that I found.
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