I've seen a test version of an app cause issues such that the launcher would crash (i.e. "respring"). Probably some intersection of particular api usage and OS bugs.
To the unobservant user it looks like the OS is rebooting, although it's much quicker than a real reboot.
psh, iOS can be rebooted from safari by web pages - just send them enough images with 3d transform + filters and watch the memory allocator kill the whole system trying to compose the thing.
Yes, I believe they can. I haven't had my iPhone (6S) crash more than 5 times that I can recall in the 14 months I have had it. Every time it has rebooted I have been in a third party app. The phone begins acting strange, gestures may stop for a few moments then it goes black and the Apple logo shows up on the screen as it reboots.
Two of them have been in the last month or so. Unfortunately the phone doesn't just reboot. It shuts down completely and refuses to boot back up with a low battery warning. I believe this is actually hardware related but I have had it crash when trying to call an Uber. I think Facebook may have caused a crash too.
Uber was especially painful because hailing taxis in my city (Seattle) is essentially impossible and pay phones are not a thing that exist in 2016. Luckily I was near a bus stop and know how the lines work without my phone.
It was a shocking illustration of how dependent I have become on my smartphone.
Evidently they can. I witnessed it myself, even did a cold start (hold power and home until you see the Apple logo) and it still happened on a completely up to date iPhone 6.
To the unobservant user it looks like the OS is rebooting, although it's much quicker than a real reboot.