Iphone screen not damaged!

I was asked to heat my iphone using hair dryer.. because my wifi button was not working!

And i heated till there appeared a msg saying IPHONE NEEDS TO COOL DOWN, and then my wifi became enable 🙂

But during heating my iphone showed up Blue Screen i suddenly out into freezer for 30sec and then it became normal but now whenever i increase the brightness those lines begin to appear.. on low brightness these line are not visible to be seen.

Will update to 8.1.3 work?

This may be because of slow speed of IOS 8 on IPHONE 4S ??