LCD and digitizer are separate on iPad mini 2 (meaning you can salvage either one given it is unbroken and functional), that long connector sits above short one is to connect LCD. Make sure LCD is still working, then all you need is the digitizer. Follow the digitizer replacement guide thoroughly on iFixit, and also go over the exhaustive guidelines written by @refectio in his answer to this question: After doing my repairs (battery and screen) I have problems
As far as I know, iPad 5 and 6 use different LCD screens (not interchangeable). I don’t know why iFixit lists them compatible, maybe I’m wrong. In any case, you should be eligible for an exchange/refund since the original LCD works but not the replacement, contact customer support and they’ll assist you with RMA.
Those are left and right signal antenna cables, MobileSentrix have them for $1 each: https://www.mobilesentrix.com/right-and-left-signal-antenna-cable-for-ipad-air-1 https://www.mobilesentrix.com/right-and-left-signal-antenna-cable-for-ipad-air
Looks like your replacement screen is defective, remove and try the old screen if it’s still around. I doubt you can claim for warranty since it’s already installed and sealed, but if you bought from vendors like iFixit or MobileSentrix who stand behind their products, they should be able to send you another replacement or refund… just make sure you always test the screen first before adhering to chassis.
A defective rear camera will cause the front to malfunction too, you need to open it up and replace that rear cam. iPad Air 2 Wi-Fiの背面カメラの交換 Follow @refectio guideline for re-assembly in his answer to this post: After doing my repairs (battery and screen) I have problems