Q:

iPhone SE touch recognition and battery problem

Recently, I purchased an iPhone SE, 32GB, on 13/10/2018. The manufacturing month written on the box was Aug/2018. The phone came with pre-installed iOS 11.4.1 and on the same day I updated it to iOS 12.0.1. 
I am facing some major issues with touch and battery backup. I also do not know how the iPhone was performing in iOS 11.4.1, since as soon as I opened the box and set all things up, I updated it. 
The issues are: 
1) Touch Screen Problem: The upper left corner (where the back arrow of most of the iOS apps is situated) fails to register the correct position of a touch. Tapping the arrow right on it does nothing. I need to tap little bit to the right of the arrow. This is also same for the upper right corner. In this case I tap a little bit to the left instead of touching the exact location of the target. This is extremely annoying. 
Tap targets which are minute in size require several taps to activate. Surprisingly, this is not true for all the small-sized targets. Some small-sized target can very easily be activated without any false tapping. 
For example, in the Weather app, the "Add city" option (plus sign inscribed within a circle) requires 10-15 taps to activate, and still, I am searching for the right spot for it. This is same for a small "More" target which appears on the right side when an app is being updated in App store. However, a very small cross arrow which comes on the right side while typing in the search bar of Safari is extremely fast in recognizing a touch. I do not know whether this is a software issue or a hardware one.
This is also happening for third party apps. In Messenger, if I tap the account info button (the very small circle on the top left corner, which contains the profile picture), nothing happens. But if I tap slightly to the right of it, the phone recognizes the tap. In the Twitter app, the account info button (placed exactly at the same location as in Messenger) easily recognizes the touch. (However, the size of the info button is slightly bigger in Twitter than that of in Messenger.)
Deleting the first row apps in any of the home pages is also troublesome. Tapping the cross mark on the app icon does nothing. I need to tap little bit below the cross mark. This is true for any app which I place in the first row. Deleting apps in other rows is, however, normal.  
There are a number of examples can be provided regarding this calibration problem of touch.  
2) Battery life: In short, really bad battery life. Today (24/10/2018) I got a "Screen on time" of 6 hr 20 min, during which the battery percentage went to 5% from 100%. The total time including the "stand by time" is 15 hr 40 min. At 08:00 hours battery percentage was 84% and at 16:40 hours it came to 5%. For this entire discharge cycle (100%-5%) I kept the phone in low power mode.
Is everybody with an iPhone SE on iOS 12.0.1 facing the same problem with touch?
Is battery draining more in ios 12.0.1 compared to ios 10.3.3?

A:

iOS 12 should bring better performance and battery life, not make it worse.
Since you have just recently bought the device, you should tell whoever sold you the device that it has these defects and request to exchange/return the device for a new one. You should probably hurry before you run out of time to return it.

