Simple CTF Hints

Challenge 1 - FTP

If you have a fully working Internet connection, this challenge should be trivial. However, many networks provide only partial or intentionally restricted connectivity. This challenge aims to demonstrate how those deficiencies or restrictions can prevent some things from working.
You should use a fully operational Internet connection for network pentesting, if your connection has deficiencies then you will be unable to thoroughly test targets. Scan results can also miss things due to your own broken connectivity rather than configuration of the target systems, depending on the services and protocols being used by the target systems.

Challenge 2 - HTTP

For challenge 2, look at features of the HTTP protocol. Don't concern yourself with the page content, the flag will be obvious once you send the right combination of HTTP parameters.

Challenge 3 - HTTP again

This challenge is similar to challenge 1, with a sufficiently capable network connection simply visiting the URL is enough, however certain broken connections will be unable to access it.

Challenge 4 - HTTP yet again

Challenge 4 is a combination of challenges 2 and 3, you need a fully working internet connection as well as an understanding of how the HTTP protocol works.

Challenge 5 - Email

Challenge 5 is similar to challenge 2, but adapted to email. You need a modern fully functional email provider and then it will work trivially. Gmail would work, but is explicitly blocked because that would be too easy. Office365 would work too but not with the default configuration. Other providers YMMV.