When force or violence is used by an unlawful assembly, or by any member thereof, in prosecution of the common object of such assembly, it constitutes the offence of:

Hiring or conniving at hiring persons to join an unlawful assembly is an offence punishable under which Section of the Indian Penal Code?

'X' threatens 'Y' that he will post defamatory statements on social media unless 'Y' pays him money. Which offence under the Indian Penal Code has 'X' committed?