Is he who trims his beard and does not pray at night sinful, knowing that growing the beard and praying at night are Sunnah?

Growing the beard is a confirmed Sunnah from the Prophet, peace and blessings be upon him, both in word and deed. The correct view is that it is not permissible to trim or shorten it. As for night prayer (Qiyam al-Layl), it is not obligatory but rather a highly encouraged supererogatory act. It was obligatory at the beginning of Islam, then it was lightened. The Ahadith encourage it because it is the practice of the righteous, a deterrent from sin, a means of drawing closer to Allah, and an expiation for misdeeds.