The CTET eligibility certificate is now valid for a lifetime for all categories.
Earlier it had a limited validity of seven years, but that rule was changed.
Qualifying once means you never need to reappear for the same paper level.
Remember: CTET is only an eligibility test, not a recruitment exam.
You still need to apply separately for teaching vacancies in schools.
Paper I is for Classes I–V and Paper II for Classes VI–VIII.
There is no limit on attempts, so you may reappear to improve your score.