Q: How can i remove restricted area which is previously set for Guided Access?

If you're using Touch ID on your iOS device go to Settings > General > Accessibility > Guided Access > Passcode Settings and turn on Touch ID. Now, when you're using Guided Access, you can end the session by following these steps:

Press the Home button once. Use Touch ID.

If you're not using Touch ID on your device, follow these steps to end a Guided Access session:

Triple-click the Home button.

Enter the Guided Access passcode.

Use Guided Access with iPhone, iPad, and iPod touch - Apple Support