Q 1: There is a statement that says:
"Good will remain in me and my Ummah (nation based on one creed) until the Day of Resurrection."
Is this saying a Hadith?
We do not know of any Hadith with that wording, but the meaning conveyed is correct based on the Saying of Allah (Exalted be He):
You [true believers in Islâmic Monotheism, and real followers of Prophet Muhammad صلى الله عليه وسلم) and his Sunnah] are the best of peoples ever raised up for mankind
Also, it was authentically reported that the Prophet (peace be upon him) said:
A group of people from my Ummah will always remain triumphant on the right path.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.