Dependent Income - How to filing tax?

I claim my father-in-law as a dependent while filing tax year 2020. He's 71 years old. This year he earn around $3,500 (estimated by end of 2021).

 

My questions for filing tax year 2021:

  1. Am I still eligible to claim my father-in-law as a dependent?
  2. Do I need to include his income while filing tax year 2021?
  3. Does my father-in-law need to file his own tax 2021?