Multilingual and Multi regional Support

Please help me and pardon my terminology as I’m still very new to all of this.

I have a Language learning website I’ve created with WordPress and I’m using Rank Math for the SEO.
Although I have a drop-down Language selection plugin, from my understanding Google an other browsers won’t recognize this Globally or as a Multilingual site and I need to use Hreflang Tags.

Yes I understand there’s plugins such as WPML, Polylang, Gtranslate etc that have a premium feature to get you’re site Global or you can purchase domains in every single region that you wish to Geo-target, all of these options are far outside of my budget.

I have followed this link mentioned by Rank Math in a previous post, to generate Hreflang tags. Hreflang Generator

(I have put the Generated code in the Sensitive Data section)
From my understanding and research, I need to use sitemaps and not HTML header code. As I’m already at a dozen various languages and regions, With the possibility of further expansion. From my understanding, adding this to the header of each page would only bloat my page sizes.

My Questions are;

1) If this code is correct, How and Where would I implement this Sitemap code within WordPress or Rank Math?

2) I read that each page/content in each Language/Region needs to be canonical for it to be index in that Geographical region. Is this code properly doing so?

3) I also read that you need to have a “x-default” value for Languages/Regions not supported. I’m very confused as this Sitemap code makes no mention of such. Is that “X-value” only pertaining to HTML or am I missing something from this Sitemap Code?

4) If I go to edit my page in WordPress > click on the Rank Math settings. ( E.g. Edit snippet, Focus Keyword etc..)
I was able to score a 90/100 on my main page which is in my native Language English.
If I follow the exact recipe I did on my main page for any other Language variation of the same page, I can’t seem to score anything higher than 74/100 no matter what translation and other words I try to use.
From reading other support post, I understand that the scoring is a general guideline but I would still like to try my best to reach 100/100 to best optimize my business for Global usage.

5) In regards to further expansion, would I need to redo this entire process or simply edit the code in the future if I add additional Languages/Regions? Also is Hreflang only pertaining to Google? Do I need to follow a similar process for every single browser out there, to get my site recognized as a Multilingual and Multi regional website?

Thank you for your time in addressing these Questions.