The list for dormitories in Tokyo can be found HERE.

The food served are not halal at the moment.

That being said, you are allowed to use the common kitchen to cook your meals.

Cooking in your room is strictly prohibited.
※ Rooms in the provided list do not have a kitchenette.

Cooking can be done in the common kitchen which is available in all dormitories.

No, changes are not allowed once the dormitory is selected for you.

You can choose to proceed with the selection given, or cancel your application altogether.

Futons can be purchased online and delivered to your dormitory.
Most online shopping platforms in Japan allow you to choose the specific date (and time) you would like your items to be delivered.
※ Please do not have your items delivered earlier than your move-in date as it may be rejected by the dorm managers.

You may purchase the futon by yourself, or seek assistance from A to Z Language Centre.

The reasons may differ, but most of the time it is due to late submission and no vacant rooms available at the time of application.