Apple has a feature called ‘Guided Access’ that allows you to temporarily restrict your iPad to a single app (i.e. ReadyMind).
If you have activated Guided Access before you pass your iPad to a client to complete the assessment they will not be able to exit ReadyMind. Only you will be able to deactivate Guided Access with a passcode.
When using ReadyMind on an iPad we recommend you become familiar with Guided Access so you can have an extra layer of security and your clients can’t access other data or apps on your iPad.
Instructions to set up Guided Access on your iPad can be found here:
https://support.apple.com/en-au/guide/ipad/ipada16d1374/ipados