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I got him to understand.

I made him understand.

I had him understand.

I know no 2 is used most frequently. But what about no 1 and 3 please explain the meaning.

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(2) feels more forceful than (1).

(3) is not a likely thing to say.

Comments  
Students: We have free audio pronunciation exercises.
Yeah have and had is like to give command or request to someone and you can't command or request to someone to understand something.
But still I am having a hard time learning the usage of have in causative sentences.