When I was playing I realised that sometimes when I ate an apple in Twin Mode and I inmediatly press the key in the direction that the snake will go. The snake gets like a push. I don't know if someone has seen that or I am just bad.

Nope, it's just a well-known trick to skip the twin mode animation. I can't recall exactly how much time it saves by itself but it does add up if you do it on every switch