Dogmas are moral principles and doctrines that were taught by Christ, by the Apostles, and having come from the Church. The dogmas of the Church are in both the creed above, and the canons of the seven ecumenical councils. 

Historically, the Nicene Creed was used both catechetically and before baptism to ensure that people understood the foundation of the Orthodox Christian faith. While it is still used in that way today, it’s also used in liturgical services.

So it is neither a simple confession or statement of faith, but a dogmatic creed.

The book you need to read given the questions you have would be Exact Exposition of the Orthodox Faith by St. John of Damascus. It was written in the 8th century and everything in this book the Orthodox Church still fully adheres to today. He summarizes most if not all of the Church’s dogma here.

https://stanthonysmonastery.org/products/exact-exposition-of-the-orthodox-faith

There are free versions online if you prefer that.