Question regarding custom pages and Argo

Hello,

For those of you who are using Custom Pages, " Personalize the error and challenge pages that Cloudflare presents to your visitors.".
I see that instead of uploading the HTML you need to provide Cloudflare with an URL, does that mean Cloudflare will query my backend for each request received on any of the customized pages?

At the same time, I was wondering, if we suffered a traffic spike due to HTTP attack, is it billed? Cloudflare states on their page that no traffic from DDoS will be billed, however, I’m not too sure that applies to HTTP attacks.

I wanted to refer to support initially, however, it’s been two days and my ticket did not really progress, unsure whether if I’m not explaining myself well or support is focusing on other matters.

Regards.

My support ticket is still not answered, the supporter that initially replied seems to have vanished.
The “median” ticket response time is supposed to be ~6 hours, however, we are about to reach the forth day with no updates for questions that I believe are fairly easy to answer?