Yes, you can most likely use your existing Armed Forces certificate from last year for UPTAC/AKTU and HBTI counselling this year, assuming it hasn't expired and meets the eligibility criteria. These certificates typically don't have a short expiry date. They are issued to dependents (children) of defense personnel and remain valid as long as the parent is in service or a pensioner.

UPTAC/AKTU and HBTI counselling generally consider Armed Forces certificates issued in the past for claiming reservation benefits under the "Defense" category (nomenclature might vary slightly).

https://engineering.careers360.com/articles/uptac-barch

I hope it helps!