Is it possible for a young man at the age of 21 or after obtaining his high school diploma to begin studying Fiqh (Islamic jurisprudence), Seerah (Prophet's biography), and Sunnah (Prophet's traditions), and will universities accept him at this age?

The appropriate age for seeking knowledge is the age at which a young person reaches mental and physical maturity, enabling them to comprehend different types of discourse and endure hardships. This age varies from person to person, but twenty-one years old is considered suitable in all cases. A young person should hasten to seek knowledge due to the Prophet, peace and blessings be upon him, saying: "Whomever Allah wishes good for, He grants him understanding in religion." Also, because knowledge is a path to fearing Allah, as Allah the Almighty says: "It is only those who have knowledge among His servants who fear Allah," and the Prophet, peace and blessings be upon him, said: "Whoever takes a path seeking knowledge, Allah will make easy for him a path to Paradise."