yes, you have to do the calculations to guarantee the same number of moles of iron.

Yes. You can use anhydrous ferric chloride. The key point is the equal molar amount of iron.

Yes, you can do that but you should put in your consideration to repeat your calculation of the weight you use to prepare the molarity you need according to the new molecular weight of anhydrous salt instead of the hydrated one.

Good luck

Yes you can ! But you have to confirm it by calculation to proof the same numeber of moles of iron.

Yes, you can use it but you must calculate the necessary weight you use to prepare the molarity you need