From the Instagram Help Centre page (same page link you have given in your question):
You can always report strange emails to firstname.lastname@example.org.
So, you don't have to click on the link in your email. You can forward this mail to Instagram directly.
Yes. So long as you are interested in the followers of Instagram accounts you know, this is possible. While a request to that URL will only return 100 followers, an automated repetition of that request along with some kind of scraping of the results modal will give you a full list of followers.
One way to accomplish this automation is by using PhantomBuster'...
Instagram has an API that you can use that might suite your needs. It should work in whatever language you want to use as long as it has the ability to consume an API.
Any questions about how to use a language to query the API would need to be posted on StackOverflow and not here.