Question

If my granny (forget) to do that I (remind) her about it

Answer 1

If my granny forgets to do that I will remind her about it. ( Conditional I)

If my granny forgot to do that I would remind her about it. ( Conditional II)

If my granny had forgotten to do that I would have reminded her about it. ( Conditional III)

Answer 2

If my granny forgets to do that, I will remind her about it.