What is guided access and can I use it to lock down my iPad?

Guided Access helps you to stay focused on a task while using your iPhone, iPad or iPod touch. Guided Access limits your device to a single app and lets you control which app features are available. Importantly, you can use Guided Access to disable the Home button when using Snap + Core First or Compass to prevent users from exiting the software.

You can use Guided Access to:

• Temporarily restrict your iOS device to a single app (such as Snap + Core First or Compass)
• Disable areas of the screen that aren’t relevant to a task, or areas where an accidental gesture might cause a distraction
• Disable the hardware buttons

To enabled Guided Access:

1. Go to Settings > General > Accessibility > Guided Access.
2. Turn on Guided Access.
3. Tap Passcode Settings, then tap Set Guided Access Passcode.
4. Enter a passcode, then reenter it. From here, you can also turn on Face ID or Touch ID as a way to end a Guided Access session.

To start Guided Access:

1. Open the app that you want, then triple-click the Home button.
2. If you want parts of your screen to stop responding to touch, use one finger to circle those areas. You can move or resize the circle, or tap the X to remove it.
3. Tap Start. 

To end Guided Access, triple-click the Home button, and then enter your Guided Access passcode.

Here is the full article:
https://support.apple.com/en-us/HT202612