Dark mode changes the background and many elements of various apps in iOS from light color shades to black and dark grey. When dark mode is enabled, it provides a reverse color scheme intended to improve readability.
The dock at the bottom of your iPhone or iPad's Home Screen is where you keep (or should keep) apps that you use frequently, because the dock is always on your screen, regardless of which page of apps you've swiped left or right to. It only fits four apps and most of us use more than four apps on a regular basis, so fitting more on the dock would be useful. You can accomplish this to a degree by using a folder in your dock. It might not be worth it if you only have a couple Home Screens worth of apps to swipe through, but it probably is if you have many many pages of apps and folders.
You can drag multiple apps at once in iOS, which can make organizing a much quicker process. Instead of tapping and dragging apps one by one into a folder, you can stack many of them and drag the stack. To do this, long press an app until it "wiggles," then start to drag it somewhere. While still holding onto it, tap another app that you want to stack and it will automatically add to your stack. After the second one, you have to double tap any additional apps to add them to your stack. A number will appear on the top icon indicating how many items you have in the stack.
You can easily find your iPhone serial number (S/N), International Mobile Equipment Identity (IMEI) number, and identifier or ICCID. Follow these steps to get this information:
If your iPhone is functioning properly:
1. Navigate to Settings -> General -> About
2. Scroll down
3. The Serial Number, IMEI and ICCID are listed along with other information.
If your iPhone will not turn on or boot properly:
Your serial number and IMEI are both printed on the barcode label that's affixed to your iPhone packaging.
If you don't have your iPhone packaging: