Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature currently requires accessing the site using the built-in Safari browser.
If you are still using CentOS 7.9, it's time to convert to Alma 8 with the free centos2alma tool by Plesk or Plesk Migrator. Please let us know your experiences or concerns in this thread: CentOS2Alma discussion
I don't think you can at least on the VPS server itself. You need your VPS provider to protect the server. They do it on the switch/router level. You could protect single domains using cloudflare. https://www.cloudflare.com/ There is some other DNS services they also can help with DDOS.