You probably know by now that Apple replaced Touch ID with Face ID on the iPhone X, which uses its True Depth camera to take a 3-D scan of your face rather than a 2-D image of your finger print. The recognition software learns more as it goes and is pretty good at ID-ing you even if your appearance is somewhat altered with a new hairstyle, facial hair, glasses, a different expression or what have you.
Not the first question Apple fans would have asked just a short week ago. Pairing the iPhone SE 2 with an iPhone X-styled notch seems unlikely, as the SE has typically been priced as Apple's entry-level 4-inch device. This hasn't stopped case designer Olixar from betting this year's iPhone SE update will be a radical departure from its current design.
There remains a large gray area and many pending court cases regarding search and seizure of smartphones by the police and federal agents. Currently you can not be compelled to unlock your smartphone and police need probable cause to seize it, but border agents do not. With Face ID however, it wouldn't be difficult for a federal agent to take your iPhone and point it at you in order to unlock it. Considering how much personal information people have on their smartphones, the heated debate between privacy advocates and law enforcement is not surprising.
Occasionally a buggy app or a new iOS update will result in instability that sometimes causes your iPhone to freeze or become otherwise unresponsive. Instances of this sort require you to force a reboot (aka hard reset, hard reboot, force restart, force reboot). A force reboot will retain your data, so it's not like doing a factory reset which erases everything. Hopefully after restarting you will be able to get rid of the offending app or revert to an earlier more stable version of iOS.
If you are having trouble with double-clicking the iPhone X side button to bring up Apple Pay, you can slow it down or speed it up in Settings. Head to Settings -> General -> Accessibility -> Side Button and select Default, Slow or Slowest. This will affect the speed required for triple-clicks as well.