Is it obligatory to make up the prayers that were shortened during the investigation period in prison, based on the mistaken belief that imprisonment is a reason for shortening prayers?

If you are imprisoned in your own country, it is not permissible for you to shorten the prayer. However, if you are unjustly imprisoned outside your country and the distance of imprisonment is a distance that permits shortening, then it is permissible for you to shorten the prayer according to the Hanbalis. You are not required to repeat the shortened prayers as long as you acted upon a permissible opinion. But if shortening was not permissible, then you are required to make up those prayers according to the majority of scholars, and making them up is more cautious.