Is it necessary to put 1 tbsp of flour ? Can I use anything else instead ?

The flour in a cheesecake provides a starch that helps bind any extra liquid so your cheesecake sets up firmly. You can use cornstarch instead. Since you will be adding in orange juice, you need something to help control the liquid because it's not going to evaporate during baking as it might do in a traditional oven. You can also use a ground nut flour, perhaps almond- though this will possibly overwhelm your citrus flavor.