Learn English – Word for a person who wants to impose his rules everywhere or advise

For one-worders, I like @Robusto's "self-important" and @Nick's "presumptuous."

I'll add "inconsiderate," since I don't see that it's been added yet.

I've also described people with similar tendencies as "having an unjustified sense of entitlement," though I usually leave out "unjustified."

"scofflaw" is a fine word, but it's almost an archaic usage. I just haven't heard it in non-facetious, non-ironic usage in USAmerican language. "bumptious" falls into this category as well. Nothing wrong with the word, but not used much. It can be used. Maybe you'll use it and start a trend. Of course then it might become a cliché .

"sociopath" is probably the correct diagnosis, and so has the advantage of being literally correct. Probably a bit inflammatory (unless you mean to be inflammatory, in which case, have at it).

I don't feel "loose cannon" is correct here, unless the OP has a different sense of the person in question than I'm getting. Usually a loose cannon is someone who is institutionally entrenched and whose character is endangering either the institution or those it comes it contact with.

You could call people like that "turncoats" or "renegades." You could describe them as "dissident."

No single verb I know quite captures what you've described, but try "abandon," "desert," "betray," "defect," or "dissent."

Words that fit into the blanks in your sentences are "resents," "scorns," "rejects," and "disdains."

When someone is different from their origins, especially when a child is different from his or her parents, people say, "The apple has fallen far from the tree." There are lots of variations on the phrase "too good for," and in this context someone might contemptuously say, "They think they're too good for us now." When people mock others for qualities they themselves exhibit, like the partier who looks down on other partiers for partying, you might say, "Look at the pot calling the kettle black."