Adobe’s cloud service will process the file and open it as an document in your older version.
What you will never find is a magic wand that turns an InDesign 2025 file into InDesign CS2 for free. Adobe’s business model depends on version lock-in. However, the IDML loophole is legal, supported, and completely free.
Converting InDesign files to older versions can be a challenge, but there are free methods available. While these methods might have limitations, they can help you achieve your goal without spending a fortune. If you're dealing with complex files or require precise control, consider using the built-in export feature or investing in a paid solution.