The screen is one of the most important screens on the iPhone screen. Icons (from iOS12 and app versions) or app icons select apps.
Wait for the icon to appear with an X in the corner, hold them down and move them around the screen. If you see an icon slipping out of your hand at a point on the screen, that point is probably dead.
Another way to test for touch is to power off and restart, when the Apple logo is white with black surrounding it, and see if any dots show other colors like blue, red, purple-yellow. no... if yes, then that place is dead contact, this bug usually happens when the screen is dropped, in water, pressed, replaced with a poor quality screen...
One way to test if your iPhone display is genuine is to set it to maximum brightness and open a black picture. You can also zoom in on the image to make sure the entire screen is black. If the screen doesn't even appear to be on, you've got a true OLED display. On the other hand, if you notice even the slightest tint of gray or white, that's a sign that the monitor isn't genuine.
So, the most crucial thing for you to take apart your smartphone is still to buy a used phone, so an easy way to get an iPhone before you decide to buy it.
The long-press gesture displays content previews, actions, and context menus. If you're having trouble performing this gesture, do the following:
Go to Settings > Accessibility > Touch, then tap Haptic Touch or 3D & Haptic Touch.
Choose a fast or slow touch duration.
iPhone with 3D Touch, you can also choose the desired pressure Light, Medium or Firm.
Test the new settings on the image at the bottom of the screen.
Other Signs Your iPhone Display Isn't Genuine
When you swipe through the menu, the image will ghost or leave marks.
An overly bluish tint is visible on the screen. Or the monitor appears yellowish due to incorrect monitor color calibration.
There is a noticeable color mismatch between the home button and border color.
The receiving grid is aligned perpendicular to the surround. On raw devices, the alignment should be parallel.
The proximity sensor is split in two, with purple and shiny colors.
Aftermarket screens are often taller than original Apple monitors.
Adhesive-based dust collectors generally tend to stick to the screen longer, possibly due to a poor or lack of oleophobic coating.
If you put a note on the screen and shake the iPhone, the note sticks to the screen with no problem. On a real monitor, sticky notes shouldn't stick to the glass.
However, keep in mind that the results of this test are not very reliable if the device has been used for a long time. After months or years of use, the device will no longer have an even coating. Multi-Touch is unresponsive in some screen areas.