Adobe never released an official portable version of InDesign CS6. Any "Portable" copy you find on torrent sites, file forums, or blogs is unauthorized. These are cracked versions where the activation mechanism has been removed or emulated.
1. Legal & Ethical Gray Zone
2. Stability Issues
3. Feature Obsolescence
4. Workflow Friction
5. Security Risk
If you have a decade-old .indd file that crashes newer versions of InDesign, CS6 Portable might open it reliably. Adobe InDesign CS6 Portable
You could import a PDF form and add interactive fields directly in InDesign.