1) What's the difference between GET OUT OF/GET OFF ?

Like in: I go out of the car/house. Could I use 'get off' as well?

2) Are they both ok?: I helped him do the homework/ I helped him TO do the homework.

3) After consulting the dictionary, I've found thet THEREBY and THEREFORE mean the same, but I guess there must be some difference in terms of register or place in the sentence where they are placed. Or maybe I'm wrong?
My point of view is - maybe you mean go out of and get off or I don't understand you very well but - get off means that somebody else tell you to leave the place or to leave him alone get out of means that it is not necessary to leave the house if you don't want and nobody tells you to leave the house.
In the second sentence I suppose that the second is correct but I am not sure
As far as I am concerned thereby and therefore
thereby translated form my dictionary in this way therefore - because of that !
I think "get off" is mostly used when talking about means of transport: we get off a car, a bus, an plane...
When exiting a place, it's usually "get/go out of"
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Dear EyeSeeYou,

I get off the bus.
I get off the train.
I get off the plane.
I get out of the car.
I go out of the house.

Best wishes,
1) In their most literal uses, "get out of" means to exit -- or cause to exit -- from an interior space, and "get off (of)" means to leave -- or remove from -- a surface.

So you get out of a car or out of a house, or get something or someone out of a car or house. These are interiors, enclosures, or containers. Opposite of "get in(to)".

You get off (of) the couch or get off (of) the table, or get something off the (surface of the) couch or table. Opposite of "get on(to)".

The house is on fire! Get out at once! And get the children out of the house!
The children ran to greet him as he got out of the car.
If you can't stand the heat, get out of the kitchen!
The auditorium was stifling. At the end of performance everyone rushed to get out.
I got my old photo album out of the drawer and showed it to everyone.
After we finished the job, we had to get the excess paint out of the containers.

I couldn't get the stains off the plates.
Get off (of) my property right this minute, or I'll call the police and have you arrested for trespassing!
There was something very wrong with the engine; the plane could not get off the ground.
Get your lazy *** off the couch and do some work around here!
Susan used a new cleaning product to get the dust off (of) the books.

2) With the verb "help" that "to" is optional.

3) "therefore" and "thereby" are different in meaning, the difference hinging on (obviously) the difference between "for" (as in "for that reason" and "by" as in "by so doing")

"therefore" makes a conclusion.

I was sick; [therefore / because of that (fact) / for that reason / so], I did not go to work.
The legal drinking age is 18. Sam is 16 and is drinking. [Therefore / because of that / for that reason / so] Sam is drinking illegally. [Generally followed by a full clause]

"thereby" refers to the way something is done. It tells us that the preceding fact(s) describe how the following facts come to be. [Generally followed by a gerund]

He placed himself directly in front of me, [thereby / in that way / and by doing that] preventing me from reaching the money.
The detective finally found the missing knife, [thereby / in that way / and by doing that] solving the murder mystery.

I totally agree with what CalifJim suggests for 2) and 3).

The 'to' is optional with the verb 'help', and 'therefore' is different from 'thereby'.
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QUOTE: Get off (of)

Is "off of" ever correct? I've noticed its use in the USA and in certain English dialects but it's generally not accepted English (British) usage.
I think it's considered incorrect in British English, but it's OK in the U.S.

And yet -- weren't the Rolling Stones British? Old song: "Get Off ofMy Cloud!" Emotion: wink

I think they spent too long in America on drugs!
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