iPhone broken
Hi my apps aren’t opening and my power button doesn’t work. Not on this iPhone on a different iPhone
iPhone 6s, iOS 15
First try a forced restart, but as that entails using power button it may fail and a repair will be needed. Try it anyway.
Forced restart
https://support.apple.com/guide/iphone/force-restart-iphone-iph8903c3ee6/ios
How to arrange a repair
https://support.apple.com/iphone/repair/service
Anything other than Screen or Battery may be a replacement phone and the price is in the article.
You can see additional service information within the following article:
Prepare your iPhone for packing and shipping