This plugin can be easily implemented in any other custom form.

How to Show:

If you have a php form (where you can add php code) then add do_action( 'anr_captcha_form_field' ) just before your submit button

OR

If your form can parse shortcode then add [anr-captcha] just before your submit button

How to Verify:

To verify use anr_verify_captcha(). It will return true on success otherwise false.

Example:

if ( anr_verify_captcha() ) {
    // Answer is right
    // process form
} else {
    // Answer is wrong
    // Show error or take other necessary action
    // Do not process form
}