Once Adam was on Primus he stopped saying "By the power of Grayskull" and said "By the power of Eternia". According to Jack Olesker (series bible writer) the line was changed because Adam was too far away from the power source and had to rely more on his wits than his brawn. However, the toyline suggests that the line was changed due to Castle Grayskull transforming itself into Starship Eternia in the mini comics.
He-Man travels to the distant future, landing on a planet called Primus. According to series bible writer Jack Olesker, Primus and Eternia are two different planets.
Skeletor leaped into the time machine with He-Man during a fierce battle between the two in "A New Beginning".
He was summoned by Master Sebrian and the elders of Primus because they needed his help in saving their civilization from invading mutants. It was told that they were to seek the power of the good and the way of the magic. He-Man was the embodiment of that very statement.
Only He-Man and Skeletor traveled to Primus for the bulk of the series. The Sorceress would speak to Prince Adam and He-Man via telepathy often, but she remained on Eternia. One guest appearance from Eternia, however, did occur. In the episode "Once Upon A Time", Teela is sent to the future to help He-Man.
Prince Adam assumes the role of Master Sebrian's nephew and stays with him at his home.
Mattel was very specific about which characters they wanted rolled out in the toy line and she was not one of them. This may also have been due to the complicated rights split that Mattel shares for She-Ra with another company.
Only Master Sebrian knows. He-Man reveals his duel identity to him in "A New Beginning".
In "A New Beginning", Prince Adam reveals his secret to his parents, King Randor and Queen Marlena, in their throne room. From there it was their decision as to what to do. Jack Olesker had envisioned He-Man's/ Adam's return to Eternia in Season Two, but the series was canceled after its initial 65 episode run.
Not a lot. Again, Mr. Olesker wanted to move away from sword and sorcery to sci/fi. That said, it was still powerful in battle against Skeletor and the mutants. It could deflect energy and even at times produce energy itself.
He-Man no longer calls upon the power of Grayskull, instead calling out for the power of Eternia. It was said that He-Man has the power of the good and the way of the magic within.
The New Adventures were a syndicated series, so it aired on different channels in different parts of the country. The entire 65 episode run is currently available across two DVD box sets.
One season consisting of 65 episodes.