Learn English – the difference between get through and get over it

Your examples are mixing two senses of the word challenging. The entry in Slovar-vocab is wrong when it states "stimulate" is a synonym of "challenge" when it means "something difficult".

1. The book I read stimulated me.
2. The book I read challenged me.

In sentence 1, the book is thought provoking or inspired interest in a topic.
In sentence 2, the language of the book was difficult and it took a lot of effort to read, or it forced me to confront my thinking about something and it was a little uncomfortable for me to realize that maybe I need to change my opinion or understanding. It's not clear from the context which meaning is the intended one.

One interesting thing to note is that while "stimulating" is sometimes listed as a synonym for "challenging", the opposite isn't usually true. They are only related through the word "provocative" which has two meanings:

1. Serving or tending to elicit a strong, often negative sentiment in another person; exasperating.
2. Serving or tending to excite, stimulate or arouse sexual interest.

"Stimulating" is provocative in a positive sense, but without necessarily the sexual connotation, like "exciting". "Challenging" can mean provocative in a negative sense, like "defiant" or "disturbing", but it usually means "difficult to do".

"To inaugurate" is fairly archaic in American English. We say people get inaugurated in political office, or to inaugurate a new policy. I couldn't tell you exactly what the difference is, but I can't remember the last time I heard someone use the word for anything but a new president.

To say something "launched" implies movement, and a certain element of risk. Its usage is metaphoric, as literally speaking only vessels launch. When you "launch" a new software, you are taking it from its safe harbor (the development team) and putting it out into the dangerous seas (the general public). It used to imply adventure and risk, but is now sufficiently commonplace that people don't normally think of it that way. "Released" is a more neutral word for the same thing.