Short answers, pulled from the story.
The Supreme Court of the United States stands as the highest court in the federal judiciary. This institution represents one pillar of a system designed to interpret, defend, and apply law for the state.
Justinianus codified all Roman Law into Corpus Iuris Civilis during the Dominate era which lasted from 284 AD until 565 AD. This collection included Institutiones, Digesta, Codex, and Novellae parts.
A revised Code of Canon Law obtained legal force on the 27th of May 1917 promulgated by Pope Benedict XV. This code replaced the previous collection that remained in use until Pentecost the 19th of May 1918.
Common law refers specifically to judge-made law where courts make law limited to facts of particular cases where legislature has not acted. Courts fill legislative gaps through prior case law interpretation while statutes are laws created by the legislature.
Japan maintains a longer selection process for judges compared to United States or Mexico requiring ten years practical experience as public prosecutors or practicing attorneys. Assistant judges complete training at Legal Training and Research Institute located in Wako before serving five years appointed by Supreme Court of Japan.