I probably mean the Lock/security screen. Although I don't have it locked. So it's the generic screen it used to go to when powering up from power off state. The one with the weather app and some app logos. The screen you get when in an app and you hit the middle button. (I call it my home screen) I must have changed a setting somewhere. It's going to the 3rd screen on power up only. It's being charged now so I can't post a photo yet.
If you pull down the notification shade, click the gear icon to go to settings, tap on device at the top and then tap Lock Screen on the left under Personalization what do you see on the right?
If lock screen is set to none then you have it disabled. Experiment with those settings.
Sorry that didnt help. Reading post 3 again you are correct that you are in fact referring to your home screen since you're referring to the screen that the tablet returns to when pressing Home.
Everyone customizes their home screens differently so I'm not sure what particular page you are expecting to get but assuming you're completely stock (not using a custom launcher) try this:
Press the Home button and then once you're at the home screen use two fingers to pinch in the middle of the screen. This will zoom you out and present you with the pages of home screen that you have. Is the page that you're looking for visible? If so, tap the little house icon at the top of that home screen to make it default. Then press the Home button.