Is it permissible for a 19-year-old who has memorized only four juz’ (parts) of the Qur’an to lead the prayer, and is the refusal of some worshippers to follow such an imam a responsibility on the imam?

If there is someone among the worshippers who is a better reciter or more knowledgeable than you, then he should step forward and you should step back, according to the Prophet, peace and blessings be upon him: "The people are led in prayer by the one among them who is best at reciting the Book of Allah. If they are equal in recitation, then the one who is most knowledgeable of the Sunnah..." Leading the prayer by someone less superior when a more superior person is present is permissible, but the one who is most deserving of leading the prayer should not refrain from it.