Hi Can I ask how to validate a response that should contain a specific AlphaNumeric code? e.g. the response should contain specifically "ABC123"

If you are using a short text entry field then you can enable the Input Maks in it. You can also use the Masked Input field.

Here is the guide: Getting-Started-with-the-Basics-of-Input-Masking

Let us know if you need any further assistance.