I heard that illegal aliens sometimes get deported outside the border. And let's assume their newborn babies automatically got citizenship. Then, what happens to those children if their parents are deported by authorities?

Is the verb "get" omitted before "hit" in this sentence? If I want to use "get" to mean "to get hit in the head", how would this sentence change?

No, the verb "get" is not omitted in this sentence. The verb "get" in this case is used as the simple form of the verb "to be". However, since this sentence is in the active form, and the subject comes first, you do not need to use the verb "get". If you wanted to use the verb "get", you would have to change the sentence to passive form. Ex: Sometimes you're gonna get hit in the head by life with a brick.

When can I use the word "notch"?

To "notch" as a simple verb means to make an indentation in something. However, in this context, "notch" has the meaning of "score" or "achieve" a certain position. You can use the verb "notch" whenever you are describing the action of someone achieving something. Ex: The soccer team notched their second win of the day. Ex: She notched the title of valedictorian.

What's a "sidecar"?

A "sidecar" is "a small, one-wheeled vehicle attached to the side of a motorcycle to hold a passenger". So when he says "sidecar" he is metaphorically referring to "the person that someone is having an affair with".

Is there any other adverbs I can use instead of "exactly"?

"Exactly" as an adverb means as stated or indicated without the slightest difference. So he is saying that this is all according to what he wanted. A few adverbs that could be use in place of "exactly" are "just", "expressly" and "precisely". Ex: This is just what I wanted. = This is expressly what I wanted. = This is precisely what I wanted.

What is skipped in front of this sentence?

"Are" are left out at the beginning of the sentence. The sentence should be "Are you ready to do this?" During informal conversations, you may notice that words are left out of sentences. This is because the remainder of the sentence can stand alone and is perfectly clear without the help of other words. Words that are commonly left out are helping verbs, articles, possessives, and personal pronouns. Ex: (Do you) Know where it is? A: How's Annie? B:(She is) Not feeling well. A: How are you? B: (I am) Doing well. Ex: (Are) You ready?