Journalism

Very valid and possible confusion. These three are inter related as well as different. However, all three are non technical degrees, yet economics goes to social science area where you go for specialisation in some aspect or do research and post graduation, etc. In mass communication, which is also social science, you may specialise in technical areas like electronic media and film production, etc. You can stay in general mass communication aka journalism as well. The third is hotel management which is bit different from the other two. Hospitality jobs are huge in number but you need to take a call as you want to go to cooking or service jobs. Instant jobs are possible in hospitality than in mass communication and economics.

Yes for sure. You can pursue Masters in Journalism and Mass Communication after graduating in any of the stream. There is no restriction as such which requires a specialized field of study during your graduation to pursue MJMC. It just requires your inner-self confident enough to be able to work hard and achieve milestones in the field of journalism.
Most of the reputed colleges like IIMC, Symbiosis University, Christ University, Delhi University, Jamia Milia Islamia, JNU accept the candidates with a minimum of 50% or 60% in graduation to be eligible enough to apply for their Masters program.
Hope the answer has cleared your doubt.
All the very best for your future.
Have a amazing career ahead.