Why can’t you restore Chess.app from a backup, or trash Text Edit? How should you check that SIP’s protection is enabled on your Mac?
Irregular Time Machine backups are one of Sierra’s great mysteries. It now looks as if they might have been fixed in 10.12.4.
A starting point for diagnosing and fixing your Mac problems, with links to key articles here.
Why does almost every Mac user use their system in an admin role? Shouldn’t macOS encourage us to be ‘normal’ users?
In an undocumented change, 10.12.4 prevents any access to reading Sierra’s log when in normal user mode – it requires admin mode.
From 10.8 onwards, you will not see the classic grey display, but your Mac will spontaneously restart or shut down. Here are the details, and what to do next.
A listing of the locations of all those apps and utilities which you can never seem to find when you want them. Also covers command tools.