Hello,
It is not mentioned in the article that these limitations are for specific IPs, so think it is a generic one for all connections regardless of the source.
Regarding stress tests, it allows you to measure your web applicationās reliability beyond normal load. Stress can be different based on the service running. For example, if we are talking about an HTTP web application, it can be sending many requests more than the server can handle to know the exact threshold that the server can receive and process under extreme conditions.
There are many tools that can be used, you will need to search on that topic to find the best fit.
Thanks,
Mohamed Salah