If i stop taking protein and never take again will the muscles developed and the weight i have gained be reduced?

Protein: If you stop doing what you have been doing to gain weight or muscle mass, your gains will likely reverse and diminish. Exercise regularly and eat a healthy diet and you wont need to take protein supplements to maintain normal weight. If you are a body builder, you may need to supplement with additional protein after workouts to maintain your gains.

You should not: We all need protein in our diet as all they are present in every cell and tissue, each one with a highly specialized function necessary for life. You need at least 0.8mg/Kg a day. If you're trying to build muscle you do need extra intake close to 1.5 mg/Kg a day. If you stop taking this "extra protein" but maintain 0.8 to 1.0 mg/kg a day you should not lose any muscle mass.