Unfortunately the iPhone 11 and iPhone 11 Pro have different lightning connector ports and are not interchangeable. Had a quick look and doesn’t seem like the 11 Pro lightning port is available from iFixit, but you could potentially find one online from a reputable reseller of OEM parts?

Faulty Front Camera/Speaker Assembly. I’m not exactly sure why it happens but when something goes wrong with the earpiece flex on some iPhones, it will trigger a chain reaction that prevents most of the basic functions of the device. This could be due to some damage to a chip on the flex which in turn is causing power issues and components aren’t getting the power they need to operate correctly. Usually replacing this flex cable will resolve the issue even if it means disabling FaceID permanently.

There will likely be one in the future on iFixit, however it's not really an easy process at the moment so not practical, especially for the DIY repairers. *EDIT: Just had a quick look and there is a guide that involves the laser machine here I'm lucky enough to work with a $4000 laser machine that is used to laser off the adhesive between the glass and frame so it can be broken and chipped off slowly. We also have to use specific diagrams when lasering or else risk lasering an antenna from the device. Then the replacement glass is glued on and bonded down. If you don’t have an expensive laser removing all of the old glass and adhesive is really tricky o do cleanly and if a small piece of glass is left there when the replacement glass is put on, it’ll all shatter and all be for nothing. It’s a pain because of the way Apple has decided to construct the device, but I’d recommend taking it in to a repair shop for this repair as they can maybe do it same day and with all the correct equipment, but without...

Can you try taking a few videos with the a)front camera b)rear camera c)voice memos/recorder and see which of those if any have weaker volume or no sound. If they're all working fine then it is probably a software related issue and you should try creating a backup of all your data and wiping the device. May help if you cannot diagnose a physical hardware issue with one of the microphones.

If you’re having trouble opening the screen of the device, double check that the pentalobe screws at the bottom have been removed and that they haven’t snapped and left a piece of metal holding the screen to the frame. The tool being used won’t make too much difference if the screen and frame are still screwed together, but the iSclack would certainly be easier to use and even just pop off the plastic parts of the screen that the screws go in. Not good if you’re using the same screen again though.

Green lines and flickering is usually indicative of physical damage to the LCD or OLED panel underneath the glass, and would most often be resolved by a replacement screen, however with the water damage there may be a little more to it. If the device actually functions completely fine now with no errors or anything you might have gotten lucky. I’d recommend taking out pretty much every component to scrub down with some alcohol based cleaning solution that’s safe for electronics, and then put it all back in with the original screen(also clean connectors of screen flex cables) and see if it’ll work. If the issue is still persisting then replace the screen and everything should be fine! If possible it may even be worth going to a reputable repair shop to see if they can diagnose whether or not it’s worth getting the screen replaced.

Can you check the part number on the replacement camera part to see if is the same as the original part? In my experience, using a genuine Samsung part can still cause issues exactly as you’re describing(hanging when switching cameras/only showing black screen) unless it’s the same part number. Only the exact same part number replacement part will work for full functionality.

As you said, this is likely due to the installation of the earpiece speaker and front sensor flex assembly. Should be easy enough to open up the device and remove the shield over the speaker. Make sure all the sensors are aligned and everything fits well(eg. no force required for it to be flush with screen), and then put the shield back on, not too tightly. Turn it back on and give it another test and see if anything has changed. Typically if the speaker is making even some noise, that means it isn’t broken and may just need to be cleaned or aligned properly. Also make sure the speaker grille is clear and clean, although that shouldn’t be an issue on a new screen.

If the replacement battery seemed to work fine at first, chances are everything is working fine and perhaps the screen had a loose connection? Hard to tell but I would suggest opening the device and unplugging the battery, then screen, and then plugging both of them back in(battery last of course). If this brings the phone back to life you may want to perform a back up of the data then factory reset the device. If possible, you could get an in-line multimeter for cheap to see how much charge the device is taking and whether the problem lies with the battery, charging port, or software. Good Luck!

Seems like this may be an Audio IC issue which has become increasingly common on iPhone 6s and iPhone 7/7+. This is not an easy repair and something you’ll likely need to get done at a professional repair shop. The audio IC is a very small integrated-circuit, hence the name IC, and it is soldered to the logic board of the device. This can be repaired or replaced by an experienced engineer capable of microsoldering for typically around $100-200.