error MT0117: Can't launch a 32-bit app on a simulator that only supports 64-bit apps (iPhone 6s)
If you change the support architectures to "i386 + x86_64" or "x86_64", it should solve your problem.
You can right click your project -> properties -> iOS build -> change "Supported Architectures" to "i386 + x86_64" or "x86_64"
With Xcode 9 it should be possible to install simulators back as far as iOS 8.1 - a least that's what the "Components" tab says in the Xcode preferences.
I don't use the simulators regularly since at my company we have a couple of test devices with all our supported iOS versions and i trust testing on actual hardware more than testing on simulators.