Firefox is a web browser - the "product". Mozilla is the organization that builds Firefox.

For the most part, 3rd party developers create virtually all Firefox extensions. To date, I can probably count the number of extensions that Mozilla has actually created on two hands, and maybe one foot for the recent features that Mozilla has turned into extensions. And that is out of (probably) over 100,000 Firefox extensions that have ever been created in the last 14 years.

If you want an extension, ask someone to create for you, or do it yourself. Firefox is open source software, the information about how to create an extension is out there. Just a matter of locating the resources that would tell you how to do it.

With recent changes to Firefox, some Chrome extensions will work in Firefox right out of the box, while other may require some "translation".

You could try this Firefox extension and see if that Chrome extension works in Firefox. https://addons.mozilla.org/en-us/firefox/addon/chrome-store-foxified/ See this too: https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Porting_a_Google_Chrome_extension

And this Google search for Chrome extensions for Firefox has more resources about this topic.

There are quite a few Instagram extensions working with their API. However after few "hate" waves from Instagram most doesn't work anymore. I am using the free Instagram likes extension from Free Likes Club at https://www.freelikes.club

Not sure but I think that recently hootsuite has added Instagram and you can control post with their extension too.