The add-on Language Manger can help you with copying languages, but I don't think it can copy a whole site in one go.

Have you considered using a fallback language instead of copying the language, see https://support.optimizely.com/hc/en-us/articles/4413200653325-Fallback-languages?

I would highly recommend using fallback so you dont duplicate the content, that way you keep both content maintenance costs low as well as having an easy way to see if content is actually different in that site as you can then localise it (you can see easily in the page structure and via code).

We have used fallback for 100+ cultures and it has worked very well.

From what I understand about Fallback Languages, a fallback language is if let's say content is NOT available in Russian then it will use the newly created language site. But what we need is we need to copy the entire russian language site to another language? we are basically just trying to change the russian abbreviation?

That's not how fallback languages work. It's the other way around. If you have Spanish as a fallback language for Portoguese, then content that is not translated into Portoguese will be displayed in Spanish.

But then, will the site display the new language abbreviation?

https://qntm02mstr2ij5p7inte.dxcloud.episerver.net/kz? It shows up as https://qntm02mstr2ij5p7inte.dxcloud.episerver.net/ru/ where ru is defined as the fallback language. Shud I be using replacement language instead? When pages are not translated, it is just loading the replacement language site URL. We want the page to load with the new language as site url

You will stay on the same language segment in the URL for a fallback language. Replacement language is something else. See https://support.optimizely.com/hc/en-us/articles/4413200653325-Fallback-languages