Is it obligatory to study all madhhabs (schools of thought) and understand their differences in order to convey knowledge, or is it sufficient to apply what has been studied within one madhhab, and is there a sin for not conveying it?

A beginner student of knowledge is not obligated to study all the jurisprudential schools of thought. Rather, he should limit himself to a concise jurisprudence text within one school, and then gradually progress to more expansive texts, and then to comparative jurisprudence. This is because expanding too quickly at the beginning can lead to a loss of understanding and precision. It has been said: "Whoever seeks knowledge all at once, it will depart from him all at once," and "The congestion of knowledge in the hearing leads to a misguidance of understanding." It is not obligatory to convey everything one learns, and there is no harm in conveying what has been learned.