First of all, I dont like Tang San, although he is the protagonist of the Douluo.
His character was already molded by the "Tang Sect" an 'Assassin' organization. Do you think he can change his character just because he became child again?? a big fcking NO! There maybe some 'Character Development', but those development will only add to the current one but at the core, he will still follow his Tang Sect teachings. Because, he is a Sect slave, he will not share anything fundamental and core Techniques if they didn't join 'his' Tang Sect. I may be bias, but that's what I thought of this fcking 'Protagonist'.