Descending simulation

For my first iOS game, I wasn’t to simulate descending underground by having a super tall background that ascends when a certain Boolean is true. I also want to have the backgrounds position to affect the characters movement ability to make the game harder as you go deeper. For this I need help with learning the following things:

  1. How to assign the background a sprite that goes off screen.
  2. How to alter what portion of the background is within the screens boundaries
  3. How to check the backgrounds current position (meaning how to change certain booleans based on where it is in comparison to the devices screen boundaries).

Thank you for your support.

try to make a small project with what you want to animate, post it, and we can figure out how to animate it.

@Paintcannon Is there anything in the link below that will help. You can scroll the larger background around the screen.

@Paintcannon - I have recently written a series of posts on a 2D sidescroller which scrolls a large map. including underground.
(start at the bottom post)