You are almost on the right track. You can modify your '.htaccess' file by adding 'ErrorDocument 403 /redirect.php' -
ErrorDocument 403 /redirect.php
SetEnvIf CF-Connecting-IP "^103\.111\.227\.224$" ALLOWED_IP=1
SetEnvIf CF-Connecting-IP "^146\.70\.102\.166$" ALLOWED_IP=2
Require env ALLOWED_IP
<IfModule dir_module>
DirectoryIndex admin.php
DirectoryIndex restricted.php
</IfModule>
Create a new file named 'redirect.php' in the same directory as your '.htaccess' file -
<?php
header("Location: /unrestricted.php");
exit();
?>
This way, when your user tries to access a restricted page and encounters a 403 error, they will be redirected to your unrestricted page defined in your 'redirect.php' script.