Is it obligatory to transmit every beneficial knowledge or Hadith? And does the one who fails to do so fall under the warning: "Whoever conceals knowledge, Allah will bridle him with a bridle of fire on the Day of Resurrection"?

You are not required to send every Hadith or piece of knowledge you learn to people. The Hadith, "Whoever is asked about knowledge and conceals it, Allah will bridle him with a bridle of fire on the Day of Resurrection," refers to knowledge that the questioner needs for their religious affairs, such as teaching a disbeliever about Islam, or a seeker of a fatwa about lawful and unlawful matters. It does not refer to supererogatory knowledge that people do not necessarily need to know.