Chosen Solution

suddenly the screen is showing horizontal silver lines in a flashing way starting from the top of screen and then touch screen doesn’t work at all

This is a problem I had on a 6 plus last year. Apparently the 6 plus is prone to “bending” which causes the LCD connectors to break or not connect correctly. I took my phone to apple and they said it would be $300 to fix it or I could get a new phone. You may want to ask a repair shop that can solder.

Apple is repairing this specific issue for $149 on the iPhone 6 Plus, you can see the details on Apple’s site below: https://www.apple.com/support/iphone6plu