Are any purchases and other preparations for the Passover to be made strictly before the Passover? If there are any necessary purchases to be made for the feast celebration can they be done during the Passover feast?

ב"ה Shalom Production of Matzo which involves baking flour with water in a restricted time is the most important product to be baked and completed before Passover because we do not want to create any chametz even accidentally. Therefore, normally there is no matzo production during Passover. However, if a person runs out of food items which are kosher for Passover, they may be purchased during Passover. The custom is to do all the purchasing before the holidays so that the intermediate days of the holidays will be properly spent and not be spent toiling and doing things we could have done before the holiday. If you mean by the Passover feast, the first day of the holiday, then one is not allowed to go shopping, because that would be desecrating the holiday. All the best