have/know all the answers
have all the answers
To be able to provide information about any given topic, or reliable advice about life in general. Why are you asking me about the afterlife? It's not like I have all the answers! I'm here because I'm going to fail biology, and you always have all the answers.
know all the answers
Also, know a thing or two; know it all; know one's way around. Be extremely knowledgeable or experienced. These idioms may be used somewhat differently, expressing overconfidence, as in Helen always knew all the answers, or thought she did, or competence, as in Bob knows a thing or two about battery technology, or ruefulness, as in I thought I knew it all about plants and then I got poison ivy, or genuine expertise, as in John knows his way around tax forms. The first term dates from the early 1900s, the second from the later 1700s, the third from the later 1800s, and the fourth, also put as know one's way about, dates from the 1500s. Also see know one's stuff; know the ropes; under tricks of the trade.