mshukhrat:
It is a shame that I get an impression that update of this website is inconsistent in some place or half complete. For such seemingly growing (??) Arduino ecosystem, some links on training materials refer to external source rather than prepared by the company. Some of those links are dead.
You need to post specific links if there is to be a chance of getting things fixed.
The Arduino is an Open Source system and a great deal of the software has been contributed by unpaid volunteers.
...R