Important - Multi-Account Unblock Requests
You have to reply on the post I linked to have your multiple accounts reviewed. Otherwise, the request is ignored
Your site is working on my end. If you are still experiencing this issue, it would mean that your IP Address likely got blacklisted by the server itself, most commonly for failed login attempts.
SQL Strict mode will not be disabled. Contact the script vendor to see if there is an option with strict mode enabled. Otherwise this script will not be able to be used with the hosting.
In response to the Cloudflare part of your question, no. The free sub domains can not be used with Cloudflare, only exception being those who had it setup with cPanel prior to server migration.
You must post your request at that link as the error message instructs. That is the only way it will be reviewed.
https://community.x10hosting.com/threads/multi-account-unblock-requests.209963/