Replacing Touch ID/Home button on an iPhone 7
can the Touch ID (or Home button) be returned to life if I bring it to the Apple Service Center?


Yes, you can take your iPhone to any Apple authorised service centre to get the Touch ID/Home button replaced.


  Touch ID on an iPhone 7 cannot be fixed once and for all because theres some kind of one-to-one binding between the device and the Touch ID.


Touch ID is bound to the secure enclave built into iPhone (a security chip). Thus, if the Home button with integrated Touch ID (iPhone 5s and later) in an iPhone is replaced by an un-authorized/3rd party service provider, the Touch ID doesn't function. This is by design and is meant for keeping the security of data on your iPhone intact.


  I'm thinking that if the clickable Touch ID in iPhone 6s can be used as a replacement for the Home button in iPhone 7. Will it work?


No, you cannot use an iPhone 6s Touch ID/Home button with an iPhone 7. They are vastly different both in technology and working mechanism. (Home button in an iPhone 7 doesn't mechanically press, but instead give feedback via heptics.)