iOS app - on quit ask for password

I am building iOS app for promo. The client asked that people using it should never quit it, so I got an idea.

When people are trying to quit, they would be asked to enter the password, otherwise it's impossible. Is there a solution to this?

I would appreciate any help, thanks!

Here are the steps to easily disable the home button :

1. Launch the Settings app from the Home screen of your iPhone or iPad Tap on General.
2. Scroll down towards the bottom of the screen and tap on Accessibility.
3. Under the Learning section, tap on Guided Access.
4. If it's not already, turn the toggle next to Guided Access to the On position, then choose a passcode.
5. After having deployed your application on the device, open it and triple tap the home button.
6. Set your options and then tap on start.

You can leave the guided access mode by triple tapping the home button again, it will ask you for the passcode you set before.

Here is a link for more details (and illustrated with photos)