According to his responses to the New York Times, Yang supports single payer. However he would not eliminate private insurance, he just thinks that the health insurance industry wouldn't last long with free government health care. So it sounds more like he supports a public option and "the market" would make single payer happen.
Yang is pro-choice.
Yang has a climate change issues page but does not mention the IPCC report, its targets, or the Green New Deal at all.
Yang did not answer questions from 538 but his website does state that he supports marijuana legalization.
According to his website he supports campaign finance reform but has not stated anything about breaking up monopolies.