Did you check Ahrefs DR? They have quite complex data collection, so it's not a bad idea to check if you want to compare the easy and quick way (although it doesn't mean...

You should contact your developer to fix it.

I did not know that concept of bot-traffic, but in the last couple of days I saw some people there from random countries only on the home page that didn't seem humans vis...

Check if it was a bot-traffic or black-hat-seo. Later Google might have detected and then rankings dropped.

A canonical URL such as "domain.com" is aligned with standard website structure and best SEO practices, thus enhancing readability for search engines. It is pos...

Guest posting, Contractual Backlinks is significant for SEO backlinks. Thanks

Backlinks are an essential aspect of search engine optimization (SEO) and play a significant role in determining the visibility and ranking of a website in SERPs. Here ar...

Determining the canonical version is essential for consistency. Please specify the context or content in question, so we can establish the primary or authoritative source...

Wildcard, you should use a wildcard certificate. Here is more details, https://www.digicert.com/faq/public-trust-and-certificates/what-is-a-wildcard-certificate

Developer can fix this issue of URLs. By the way, follow Google's instruction and make the domain.com/ as frontend or homepage URL. Rest is duplicate to this URL.