Can the property management company decide the use of the basement?

Whether there is a clear stipulation in the contract or not, the property has no right to do so. The best way is to jointly sue the property with all the owners. The right to use the vehicles stored in the basement belongs to the community owner. Property has no right to change without permission.

To rebuild, only with the consent of all owners can the property have the right to do so.

The basement where cars were stored was transformed into a hotel. The state has no law to classify property.

Just sue. Absolutely win.

You can ask the property to restore the basement to its original state and compensate the related losses.