Not really sure what you mean by 'fullness' but if you're just doing curls with your hands supinated then it'd be worth doing some shit with a neutral grip (e.g. hammer curls) as that uses more of the brachialis. If you can't go to a gym/afford a bench and that then get two chairs and do fuck loads of dips between them. If you can do sets of 50+ then your triceps shouldn't be too small. Lifting doesn't stunt your growth and it'll only cause 'deformations' if you're doing something weird like focusing solely on one side of your body. It shouldn't be 'necessary' for kids to do it, because they should be really active anyway, but most kids these days, at least in developed countries, aren't. So, for them, lifting is better than not lifting. Someone that did only those three would probably have a big ass, big quads, decent triceps, decent back and decent shoulders. They'd look better than your average person, which isn't especially hard, and better than someone that just benched/curled. Would probably want to add in rows or at least fuckloads of face pulls. Deads aren't gonna be enough to address the overemphasis on pushing relative to pulling.