If your question is why some of the Mega (Ultimate) level digimon are not the same as those depicted in Adventure Tri., that is because this image was made before Tri. existed. It was made at some point in time after Adventure, Adventure 02, and the movies that are linked to these seasons aired. Agumon and Gabumon already had their Mega forms in Adventure, so these are correct. Furthermore, the armor digivolutions of Patamon and Gatomon are shown, as well as the mega forms they digivolved to in one of the movies. In the case of Patamon, that was the correct form, but Gatomon has a different mega level in Tri. The other four were probably just guesses by the artist; Tentomon and Palmon have their correct forms, while Biyomon and Gomamon don't.
Anyway, I don't really understand you. First you post a heavily edited image of Omegamon from Tri., then an image of all the main digimon in Data Squad/Savers, then some sort of promotional image for Tri. again, and now it's suddenly about the original Adventure.
That is... not exactly the usual order in which you watch Digimon. If you started watching Tri. first, I strongly advice you to watch the original Adventure first. The storyline of Tri. is mostly based on nostalgia from the first season. And if you stared watching Data Squad, then I advice you to stop and watch the first four seasons first. Of course, you are free to do what you want, but as you are new to digimon, I suggest you start at the beginning, and not at the end.
What do you think?