@luckynasan
Honestly I don’t know how to answer the first one and about the second, I don’t have any other website.
But as far as I know, my website does the following through a plugin: “Hummingbird stores static HTML copies of your pages and posts to decrease page load time.”
That’s the only cache related feature that I added (I tried cleaning the cache but it didn’t work)!
About Firewalls and security measures enabled, I believe not. The plugin worked perfectly fine last week, por example.