Chosen Solution
It’s almost sure that the cause of they issues you’re encountering is the water that found its way into the phone. The rice trick is just a urban legend, it temporarily removes moisture but it doesn’t dispose of liquid residues on components and over time it’s almost sure your device will eventually break. Liquid damage on small complex electronics needs to be taken care with proper tools by pros who can bath the phone with ultrasonic and chemicals after removing the soldered metal shields. Restore won’t probably have any effect on your iPhone. All you can try to do on your own is to replace battery and lightning connector and hope water didn’t touch phone’s logic board. If you feel like doing it yourself here are the relevant, guides..parts can be found on the iFixit store too. iPhone 6 Lightning Connector Assembly Replacement iPhone 6 Battery Replacement
