My 8 year old cracked a (very good) friend's teenager's iPhone 6. It is only cracked mostly at the bottom around the home button and just barely in front of the actually display so they said not to worry about it (I did mention that it is a VERY good friend, right?)
Anyway, I am going to replace the screen (have done several iOS device screen replacements) but I found one that says to make sure that the phone still has iOS 8.x, not iOS 9. Why? I don't want to "fix" the phone and make it not-upgrade-able. That is not really fixing it.
In my searching I have found old postings about screen issues but none ever seem to be tied to an iOS version.
EDIT: The vendor SPECIFICALLY says:
This screen just fits for the IOS 8.3 SYSTEM,the original version,but not fit the newest IOS 9.0 system. Please make sure your Iphone keep the IOS 8.3 system before installation.
Is there any firmware on the screen itself? It is on eBay so I have used the "ask seller a question" but not sure how thorough/technically sound their answer will be.
EDIT 2:
The vendor's reply was what I expected, not helpful. Just regurgitated the same statement worded slightly different even though I specifically stated that I am tech savvy and would like a detailed, technically sound answer.
As I continued on my quest I thought about the fact that the phone was still under warranty and I did not want to void the warranty. My friend has "Apple Care" and had already used one screen replacement. He used his second one for this (I paid the $80 + tax + gas money) and told him if it happens again I would pay the difference between the "Apple Care" cost and whatever they charge him so that it won't be any difference out of pocket for him.
Best Answer
There is firmware on all replacement parts. I'd just wait until iOS 9 comes out in September to make sure that the screen is compatible with the new software, just make sure you can return the screen. However, there are some better vendors, like iFixit, that would likely sell screens that will likely be compatible with iOS 9, just be prepared to pay an arm and a leg.