The front camera and the sensor on the screen are only compatible with the original motherboard they are tied together. I would check your contacts/connections and make sure you dont have a bent pin or a dirty connection. I would also check the cable from the sensor were it makes the 90 degree turn that's the spot that is easy to tear. I can't remember the name of the sensor on the screen I had a stroke a few years ago and sometimes I can't remember names and words but I know that you know which sensor I was talking about. If you are good with microsoldering you can change the chip onto a new cable and it will work.
It will transfer the serial number from the old screen to the new screen so it will keep tru tone. You can also transfer the serial number from the battery I'm not sure if it will turn off the notice that it's not the original battery. You can also transfer the information for the tapic engine so. It will keep some features. The home button you can transfer the information and it will keep some features but it won't make touch Id work and it has to be their home button brand. I would like a little more information myself to see if you transfer the information from a battery does it show that it's factory or does it show that it's aftermarket.
Both are emissions codes did you possibly not tighten your gas cap or leave it off? And put gas in your car while it was running? These could possibly cause the codes but the p2420 this can be caused by a bad switch. I would take it to a repair shop and have it diagnosed it shouldn't cost that much. Please have it checked by a professional and don't try throwing parts at because you tried diagnosing it on Google. Just because the code says something doesn't mean that is what's wrong with it. We do know it in the emissions system but you need someone with experience and the correct equipment to diagnose it.
The only way to tell is the screen take the screen from an x and xs and you will see different mounting hole for the earpiece speaker the screw studs are different places and the screen attachments on the side and top of the screen are different places. You might also check the sim card tray and see if it has the imei number on it.
If it getting wet on the passenger floor board it's the ac evaporator drain line that's loose or plugged. It could also be coming from under windshield that's where the air comes into the car. Check if you have leaves or debris blocking the area or can cause the water to go into the vehicle. That's what I would check first
I believe that they had an issue with the iPhone 6 or 6s try putting a small magnet next to the camera and see if it fixes it if it does it needs a new camera. I would like to see what happens before I can give you a better diagnosis.