Hi ebunny. Welcome to the forum.
There may or may not be a back button in an app. If there is, it will be to move back through the app's screens. To get out of an app you tap the Home button on the front of the iPad.
If you want to go to an app you were previously running, double tap the Home button. The Mulititask bar will pop up with a list of your recently running apps in order of last run. The more recent apps will be frozen in RAM, and ready to run right where you left of. Older ones will have been purged from RAM, and may or may not have their last run state saved. Depends on whether the developer chose to do so.
To delete unwanted apps, tap and hold on any app. When all the icons start to jiggle tap on the x to delete them. You an also drag them around to rearrange them, or drag them on top of each other to create folders.
Printing is more trouble.
You either need and AirPrint compatible printer:
iOS: AirPrint 101
An app like Print n Share (works with most wi-fi printers, but must be running in the background on the iPad to work) or other printer apps (many and varied in their features).
Or you can teach your main computer to pretend to be and AirPrint printer and share it's printers; AirPrint Activator (free, limited, Mac and PC), Fingerprint (versatile, Mac or PC), Printopia (most features, Mac only).
There are a few other options, but in my opinion these are the best three choices.