Misc: of what are corolla, filament and stigma a part of?

Questions

who barely received passing grades for some of his film performances, but had a no. 1 hit with 'young love' in january 1957?

who had a major hit with joni mitchell's 'both sides now'?

who is the chief of lamaism in tibet and mongolia?

who was lord mayor of london in 1398, 1406 and 1419, and is most famous for his legendary cat?

air is 21% oxygen 78% ______ and 1% other gases?