It’s possible that you may have successfully repaired the screen but damaged the connection on the iPad itself. If it’s greyed out from my experience that generally means that someone inside the iPad is damaged. Only way to fix it is to open it up again and check

The rear camera and flash are apart of the same item, if one fails it’s often that the other one will also, you might have to replace them or you can try a reboot and see if that helps.

This is quite common, i know this might sound ridiculous but if you hold the iPad and give it a decent smack on the back it may well just fix your issue. Let me know how you go

Most likely been wet, this happens a lot when phones have been wet. Might need to be cleaned or replaced

You can load new software although you need to have some know how on what to do. It’s a big ask to have someone explain step by step. You might be better off taking it to a repair store and seeing if they can flash it for you. But if you want to give it a go you need to Download Odin (Flashing software) Find your correct firmware for your device (Google) Download said firmware Put your phone into download mode (Volume down + Home button) Connect your phone to your PC via Cable Open Odin with phone connected and import firmware into AP Flash software. Make sure you have everything correct otherwise you run the risk of bricking your phone.

From memory i believe it could be a wifi/bluetooth connection

You should be able to use strong double sided tape and that should do the trick, just cut out around the camera etc. It doesn’t need much to hold it

It’s most likely not a very good screen that you got. You may have to try another one if you have it, are you able to put your old one on and see if that’s any better?

If you have to ask if you need to apply heat you shouldn't be doing it.

Have you tried rebooting it? Most of the time this can fix your issue