After returning back to the 300 Galaxies, Qin Feng first went to meet Chen Hui and Fan Feng Yi. He told them to wait for him and then he'll bring them back to the True Universe.
Qin Feng didn't try to break the Great Formation once again. He could have broken the Great Formation by relying on the Butterfly Mark given by Ye Zhiqui, however, if he really had done something like that, no one knows what kind of catastrophe would have befallen in 300 Galaxies.
After all, the 300 Galaxies have long become an independent Universe. Although compared to the True Universe, the laws here are broken, at the very least, for the people born in 300 Galaxies, the laws here are complete.