Create one with the only code in it being what is shown:
<?php
define('RECOVERY_MODE',True);
It should exactly be named and uploaded as:
constants.php
Once it’s uploaded, open a new browser and login to ACP. You’ll see a message about things being disabled.
Once done, you’ll hopefully be in ACP with a message saying turn recovery mode off. Simply delete that file to do that. Then you’ll just need to figure out which third party resource is breaking your site by turning them on one by one till the site breaks again.
Rinse and repeat. 🙂