Every device suffers glitches every now and then from a simple lever to global cluster of supercomputers. The more complex the device, the more likely a glitch will rear it's ugly head. Android devices are no different.
Now, to explain your particular glitches (and I can only guess here) for the alarm change, these interfaces make it too easy to change settings without much confirmation. I am constantly moving appointment times by swiping through my calendar widget. I would guess that you inadvertently switch the day to Friday only. Now, it is possible that the setting became corrupted or changed during an app update ... say for example the dev said instead of selecting m-f, it now said "weekdays" and goofed up the way the settings update, or that there was simply a hiccup while updating and it read the setting incorectly, but those are less likely.
As for the APN change, it might also be that the Net10 APN was unavailable but it could find the AT&T APN so it switched to it. Until you manually change it back or the phone reboots with the Net10 APN available, it would stick to AT&T, even though the account might not be active.
Once it's a glitch, if it repeats then it's a problem.
