My LO is turning one year soon and I am wondering if instead of changing his FM to stage 3,is it possible if I just use milk powder like nespray instead?

Like what other mummies suggested, have you considered fresh milk instead? Milk after 1 year old is just a supplement, the main source of nutrients should be from food - in fact, you can do without milk if LO is okay with it! As for nespray or formula, I'd suggest you take note of the nutrition value and instructions on nespray because some of them are only meant for 6 years old and above.