It sounds like "ghost touches". The digitizer, which picks up electrical pulses from your finger is likely shorting out and creating false touches. Has there been any physical or liquid damage to the phone? Sometimes the digitizer is simply defective, but this is more common from damage or a poorly done screen replacement.

What was the repair for - replacing the display assembly or replacing the charge port? If you had the display assembly repaired then the microphone on the front camera/proximity sensor flex assembly may have been damaged. Does the front camera and proximity sensor work okay? Or, if you had the charge port assembly replaced then perhaps the microphone on that flex assembly was damaged.

Yes, use DFU recovery. Power off the iPhone then plug it into iTunes while holding the home button down. You will see the connect to iTunes screen display. From iTunes select restore. If it gives the option to Update, try that first as it will preserve any locally stored data. I think from iOS 10 up that restore is equivalent to the traditional DFU recovery. If that doesn't work then go through same steps until you get to the Connect to iTunes screen display. From there, hold the home button down at the same time while holding the power/sleep wake button until the screen goes blank. Once it does, wait a couple of seconds the release the power button while still holding the home button down. If you get a recovery prompt in iTunes then you were successful. Select restore then go from there. If not, then try the process again.

Yes, unfortunately that's likely to happen if the back glass plate is already cracked but you can minimize the amount of additional cracking in the process. First, heat the back plate well and uniformly. It can handle a fair amount of heat and the more the better for loosening the adhesive. I like to use playing cards to slide under the glass back. They are thinner than something like a guitar pick and cause less of a lift that may further crack the back. Be especially careful in areas that are smashed or cracked and slide the playing card up along any crack lines so that the card is on both sides of the crack. The overall goal is to slide the card around to break the adhesive without lifting or prying substantially in one area. Differential lifting and pulling is what causes cracking.

Yes, that's the proximity sensor and it does stick in that plastic casing at times. When it looks like it's going to be stuck, I often try to pry the entire plastic housing up off the screen rather than try to pry the proximity sensor out of the plastic housing. Otherwise, work it out of the housing by prying all around instead of one spot or by not pulling it out by the cable itself.

There are two microphones on the lightning flex cable assembly. Perhaps they were damaged in the process of replacing or simply defective to begin with. They are on two small tabs that each mount on either side of the lightning jack. Check the ribbon for damage like scratches, tears or nicks.

iOS 11.0.3 update is supposed to have corrected some problems with iOS 11 running on an iPhone with replacement screen. It wasn't available at the time of your post. Wondering if you are up to date and if you are still having the same issues.

Did you completely reassemble the phone before trying to charge and power it on? With previous Galaxy S series phone generations I can and often do test the phones before reassembling the midframe. But I found that with the S8 and probably likewise with the S8+ that you need to fully assemble the phone first. On one of my first S8 repairs I found that without the midframe on I got an error that looked to be like the battery thermostat triangle error experienced in previous models. But when I put the midframe on, the problem was resolved. Apparently, some contacts must be made to complete a circuit. Hopefully, that is all that you are experiencing in your situation.

Jonathan, iPads and iPhones have an integrated chip (IC) called the Tristar chip that governs USB charging and recognition. If you have replaced both the battery and charge port and still no charging then it is possible that this Tristar chip has gone bad. That's not uncommon since they are sensitive to voltage surges or "dirty" voltage that most often occurs when using cheaper 3rd party charging cords. Apple charging cords and certain higher quality 3rd party charging cords have components that protect against bad voltage. The Tristar chip can be replaced. It requires microsoldering equipment and expertise though.

Before doing anything, be sure that your battery is disconnected or pulled out of the phone. In trying to remove the jammed SIM you will want to be extremely cautious not to break off any of the golden colored pins that read the SIM. They stick up at a slight angle. If you can access the top part of the SIM reader then I usually use some fine tweezers - poke them slightly into the SIM card to "get a bite" and carefully work it out by using slight downward pressure and inching it out (or rather millimetering it out). Check first to see if it is stuck in at an angle and use the tweezers to realign it before trying to inch it back out. Trying to pull it out from the end opposite of the way it went in generally doesn't work well. Just take your time. Good luck.