Hi there!

PSAT and SAT are administered by college board in the US. SAT is used for admission to undergraduate programs in the US and a few other countries. PSAT is Preliminary SAT/ /National Merit Scholarship Qualifying Test to check the student's eligibility for scholarship programs.

There is not such mentioned eligibility criteria for PSAT and no upper and lower age for the exam, but if you are above 21 years then you have to go through the verification by government .

Hope it helped to clear your delimma.