Science

Hello Pratik,
Some possible jobs include the following:
Chemistry research in industry
Non-research in industry, such as lab management, filling out regulatory paperwork, performing safety audits
teaching (at all levels)
Medicine
Law (both chemistry & non-chemistry related)
Consulting
Software/programming, for chemists who have some Aptitude & experience there
Science writing, including both technical writing & journalistic writing
Business, including starting a company
Finance & banking
Science majors, including chemists, pick up critical thinking & problem-solving skills that are valuable in all kinds of fields. Of course, it may be more difficult to convince an employer in a completely different field that you have what it takes to do the job, but strange opportunities sometimes pop up.
All the best.

Hi Aman,
A Thermodynamic cycle is just any scenario where you manipulate a system and end up bringing it back to its original state one or more times. There's an implied contrast with the environment (everything except whatever you've defined as the system) which very possibly doesn't go back to its initial state after a whole cycle of the system.
Thermodynamic cycles are important because the Second Law imposes interesting constraints on the sort of things you can do, and it often turns out that with a finite amount of equipment (your system) you can't do even approximately what you'd like except by running it in a cycle. In particular, you can't create work from thermal reservoirs at two different temperatures or use work to cool something below the lowest-temperature thermal reservoir you have without running something in a cycle.
All the best.