Is it permissible to use the money allocated for Ramadan before it begins, or must it be spent only during Ramadan?

You have the discretion to spend the money on food before Ramadan, unless the donor's intention was for the food to be consumed specifically during Ramadan, and not merely for general assistance and aid. In that case, you are not permitted to use the money for food outside of Ramadan, out of consideration for the donor's intention.