How to calculate Increasing, Decreasing and Geometrically Varying Annuities on an hp12c gold calculator in RPN mode

Hi all

I am trying to find a quick way of checking my solutions in a test for varying annuities [(IA)angle n, (DA)angle n, and geometrically increasing and geometrically decreasing annuities]. The only link I found is this which is error-prone and has logical flaws within the instructions. Moreover it does not cover all cases.