Ich habe einen jungen vs Ich habe einen junge
I know that junge means both boy as a noun and young as an adjective, and it can be used as an adjective and the noun could be omitted for example die jungen [leute] we can just say die junge, but for the “Ich habe einen jungen vs Ich habe einen junge" is it ok to say "ich habe einen junge(boy)", because I see that "ich habe einen jungen" is more common and is the actual sentence here "ich habe einen jungen [junge] and junge is omitted as the noun.

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The correct form is: "Ich habe einen Jungen." (boy) The nominative "ein Junge" becomes "einen Jungen" in the accusative.
The (nominalized) adjective "der Junge, die Junge, das Junge" is not often used. But the form would also be "einen Jungen /  einen jungen" if you refer to a masculine word. The form is mostly used elliptically, e. g.: "Ich habe im Keller einen alten (Wein) und einen jungen." In nearly all cases, the capitalized "einen Jungen" refers to a boy (in the accusative). The form "einen Junge" doesn't exist.

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