No. The first modules of every course and all the tutorials are open to everyone, with no account and no card. That is several dozen complete lessons, not excerpts.
No, and that is a choice. Everything is written: you read at your own pace, reread the passage that blocks you, copy the commands, and find a concept with a search. A written lesson can also be fixed in a minute, whereas a screen recording takes a day to redo — which is why video courses age badly.
A course is read online: ordered modules, self-contained lessons, and progress that remembers where you were. A document is downloaded: a solved lab exercise, a cheat sheet, a syllabus, a dataset. The two complement each other, and neither one requires the other.
Access to every module of every course, and downloads from the document catalogue within a daily quota. The quota exists to stop the catalogue being scraped overnight; it sits well above what normal reading calls for.
Yes. Every document has a unit price, and every course can be bought in full once and for all. A one-off purchase stays yours: it does not depend on an active subscription.
No. Enrolled students receive an access code that opens the whole course, free of charge, for the length of the term. The code is entered on the course page.
The paid modules close again, but everything you bought individually and everything you downloaded stays yours. The modules open to everyone stay open.
Yes, continuously. The courses track tool versions that keep moving — Kubernetes, Helm, Terraform, the Docker images — and the lessons are corrected as the changes land rather than rewritten once a year.