I have 2 alarms a day set for meds and both alarms were on, I had the phone shut off at work,FRA thing and my evening alarm starts going off. I pulled my phone out and dismissed the alarm and then got a popup on the home screen. It said power off or leave on but in airplane mode or leave on w/o airplane mode. I have had a lot of phones but never had this, well maybe an old BB, but not any recent smartphones.
I just set an alarm to go off every day and powered off the phone. I then watched the phone power its self on, the alarm go off then get the prompts after unlocking it. Nice to power off at night to charge and still have your alarm wake you in the morn. The phone powered on in airplane mode. The phone was not plugged in.