useless trivia: What Word Means: Skug?

Questions

Longest river of Asia, in China, about 5526 km (about 3434 mi) in length?

Lunar revolutionary who hated the handle `Why not'?

Machine that decreases the volume & increases the pressure of a quantity of air by mechanical means?

Machine used to separate the fibers of cotton from the seeds?

Madrid & Lisbon are both located near this river?