using one prefab or sound source in several levels

hi guys , maybe i should searched more for this , however i did but.... so lets me ask please that if i wanna reduce my project total size for better performance specially in mob devices , can have one prefab in several levels ? or when i build projet , should write diffrent scripts and make copy of the prefabs for each level ? and another question , does same texture for diffrent prefabs in diffrent levels affects the size of project or not .... maybe its a simple question at your sight but for me right now is a problem , really.... thanx and more