How to fix iPhone iOS 11 crashes to black screen frequently and locks up

Today, many many people got crashes black screan frequently and lock screen up. This tutorial may help fix this issue at this time.

Q: Iphone 8 crashes to black screen frequently and locks up
I am using iphone 8 and yesterday i got this issue and since then its being repeated like after each 15 seconds. I updated my ios also but still the same issue. Not able to use the phone. Posting this issue from other phone. I am really very disappointed. I hv been using iphone from last 7 years but this is something that is just not acceptable from apple.
Q: iPhone 6s Plus resetting every 2 minutes
Suddenly, my wife's phone went wrong last night when she realised that her phone was resetting every 2 minutes (or less). Now, I want to restore it but the problem is, this hasn't been backed up ever since. And I am trying to back it up but yeah, you see, it is resetting. It can't be backed up. I tried to remove the SIM and turned it on, still, it is resetting. Does any of you encounter this? What's the fix for the unusual automatic resetting? How can I back it up in this scenario?
Q: apps kicking me out and constant passcode requirement
since i started using my iPhone 7 this morning i have constantly been asked to put my passcode in. I have turned the phone off twice, done a soft reset, tried backing up my phone in both iCloud and computer via the computer and keeps kicking me out during backup. My service provider suggested i back up my phone, then reset to factory settings then back up from a prior iCloud backup. Happy to do this but thought id call Apple Support first however my phone has cut me off twice (once was after being on hold for 35 minutes). Anyone else experiencing this and what have you done to correct the problem? Currently trying to back up my phone via iCloud without connecting the computer and about to do reset but honestly i have no idea how to back up from the iCloud when it comes to reloading my phone after reset. please help.

The best answer at this time is:

Someone on a similar thread says that this has to deal with a date-based issue (Dealing with December 1st), and that many people in Apple Stores are having the same issue.
A temporary fix is to go into "Settings" > "General" > "Date and Time" > change your date to pre-Dec 1st (it's not a fix, but it should prevent your phone from resetting every minute or so).
"[...] it has been escalated to the highest levels and the Apple Store is full of people with the same problem."
"No fix at this time - but we can expect that this will get a lot of attention!" 
This our fix may help your phone working back as best condition:
UPDATE: Reboot your phone. Then go to "Setting > Privacy > Analytics " change all setting to off. If you have an app that has local notification with repeating settings (e.g. Headspace, Calm, or any other apps that use daily reminders) it will crash iOS Springboard. Disabling notifications for these apps may fix your issue. 
If you cannot disable your notifications, then temporarily roll back your date and time to 1 week ago, this will enable you to disable your notifications and then you can return to the current date and time without glitches.
UPDATE 2: After turn back the date. Many server calls will fail which means websites won’t load correctly or at all, apps may not update or launch (twitter, whatsapp) and calendar events, reminders, and messages won’t work.
Best viable workaround is to turn off third-party notifications. If you’re not sure which apps employ local, repeating notifications, turn them all off.
The soon-to-be released iOS 11.2 has already fixed this issue.

Cre: Apple Discussion