Understanding Supernova with Multiple Diagnostics

SN 1987A, a core-collapse supernova, was the first multimessenger transient in astronomy. The neutrinos confirmed the basic core-collapse model; the unexpected early identification of nuclear gamma-rays set the modern supernova engine model. Decades later our understanding of these events is still incomplete. Advancements require study of multiple diagnostics from these events, including observations of initial explosions with multimessenger facilities and shock break-out monitors as well as study of the remnants of long-past supernovae in the Milky Way. We will give a broad overview of these diagnostics, what they tell us, and prospects for detecting them in the next decade.