if i didn't use up all of the 8 units for the 2023, can I use the unused ones for the 2024?

Hi, thanks for your question,
Unfortunately you cannot use the 2023 product to file for 2024 taxes. 

The products are updated annually to account for changes in tax laws, the 2023 product would not have accurate amounts/tax rates/credits for the 2024 year. 

Thank you!

Kim