water damaged iPhone 4s

manubali811, as for missing components etc. you do want to consider posting an image of where they fell of etc. with your question. Use this guide. You did not tell us if you cleaned the phone properly. You will have to remove all EMI shields and use a high grade isopropyl alcohol and a soft brush. Use this guide for the cleaning. It was written for a 3G but all the points are pertinent to your phone as well. Once properly cleaned, replace the battery. As for the small components, yes that can be fixed but requires skills in microsoldering, as well as the right tools. As for your error 21 re-evaluate that after you change the battery and replace the missing components. Check these answers for that. Until you repair your phone it will only be a guess.