Some not really smart questions about changing vanila entity, getting player's lang and custom ropes

Hello, guys. MCreator is a really amazing instrument, I haven't enough time to touch java, so it really helpful to me. Now I have some questions about things, which I guess not possible. But maybe you know some ways and can recommend something for some of described goals:

1. Is this possible to change vanilia entity? I mean change their properties, textures, rules of appearing and etc... 
2. Especially I want to change Player - I think being able to change him and his stats is very important for finishing a lot of ideas. May I increase amount of player's hearts or wise versa? Or maybe get / change player's texture after some conditions... Turning off the mechanics of hunger & replacing it with another mechanic (not globally, only with some conditions).
3. Get language of player or get another way localize server's messages in chat  / hints

4. Generate something like rope (with my colors, degree of tension, thickness) between player and entity

   Thanks to everyone who suffered while reading my bad english. Wish dis topic could be helpful to me and to people with similar questions