Screen time restrictions
I have screen time set up on my daughters phone. But she turns her phone off so I can’t see what she is doing. Can I setup in parental restrictions to keep her from turning iPhone off or airplane mode?
Read these documents to see what can be done. I don't think you can prevent it from being turned off completely and unless I go downstairs and turn on my phone and activate Screen Time I can't check airplane mode. I'll let you check it instead. :-).
Use Screen Time on your iPhone, iPad, or iPod touch - Apple Support
Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support