The answer to your query about the largest banknote would be the Philippines 100,000 peso note of 1998. I only claim single credit. I would not have known this without a web search.

Measuring in at roughly the size of a sheet of legal paper, the world's largest single banknote is the 100,000-peso note created by the government of the Philippines in 1998. Designed to celebrate a century of independence from Spanish rule, the note was offered only to collectors, who could purchase one of the limited-edition notes for 180,000 pesos, or about $3,700.

I am somewhat skeptical that there was not something larger in the dim past. The Chinese had a note called Da Ming Tong Xing Bao Chao described as 34 cm by 22 cm. I figure that is a little shorter but slightly wider than the Philippines note.