Q: Why is my Iphone 6 Plus freezing, launching apps and ghost typing on its own????

Restore your iPhone. If that doesn't help it is a hardware issue that you won't be able to solve by installing software of any kind. https://support.apple.com/en-us/HT201252

If your device is behaving erratically these steps will usually help. They assume that all of the content you want on the device is in your library ready for restoring. If it isn't see Recover your iTunes library from your iPod or iOS device first. I would also recommend you copy everything out of the camera roll if you haven't already.

1. Backup device.
2. Restore as a new device.
3. Restore the backup you made earlier.

Otherwise it might be some kind of hardware issue as suggested above. It would be worth testing the device a little after step 2.

tt2

There are couple of threads that may be of interest. What you describe fits. This is the main one (44 pages)

Re: iPhone 6 plus intermittent unresponsive screen

It has been pretty well proven that some folks have iPhone 6 models that iOS 9.3.x made crazy - most folks don't.

Click HERE for an intelligent independent analysis.

My phone was acting this way before the iOS update. Very frustrating.