This person does not support China for not being socialist although every point in that photo supports China as socialist. Ultras always seem to contradict themselves when it comes to China showing that they do not read outside of their periphery.
On Practice and On Contradiction as someone else as said would be a good start. A Handbook of Philosophy written by B.I. Syusyukalov and L.A. Yakovleva is a decent read, though it is important to note that it is from the revisionist era of the USSR.
Stalin coined the term Marxism-Leninism. Marxism-Leninism was already in practice in Lenin's time, though Lenin didn't say his application of Marx's theories was Leninist, the same way Marx didn't call himself a Marxist. It was only after the fact that Stalin synthesized Marxism-Leninism by combining Lenin's and Marx's theories. In the same way, people didn't call themselves Hegelians or Darwinians when Hegel and Darwin were alive.