You need a whole bunch of punctuation to make any sense of what you are trying to say.
It's not "somebody" or "someone" which makes the difference. It's how you are using the word.
"Somebody, help me!" is a command. You are addressing "somebody" just like I could say "Bob, help me." "Bob" or "somebody" or "someone" is not the subject of the sentence. An unwritten, unsaid, understood "you" is the subject. The command is "(You) help me."
So, the conjugation of "help" matches the second person "you." You help.
It does not matter if you address the command to "someone" or "somebody."
In the other case "Someone helps me to finish my homework" the word "someone" is the subject of the sentence. Someone helps.
Since "someone" is third person singular, you use that form of the verb. Someone helps.
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