It would copy the form of the copied Stand and would appear in its original form (not affected by Requiem or other form changes, such as Star Platinum) and would be able to use any abilities the copied Stand could use, just slightly weaker. In the case of more powerful attacks such as Time Stop, the duration would be decreased to the amount the user would know. If IBT copied The World, it would be capable of using Time Stop, but only for as long as the user would know at the time. Once again, thank you for the questions!
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As long as the user and the target can both see each other and look each other in the eye for it to work. If IBT's user can make out the physical appearance of the target the ability would work. In the case of Achtung Baby, if the user was covered in makeup or some way the user could see or make out the face, the ability could work. As in the case of a stand like Enter Sandman, both IBT's user and Enter Sandman's users would need to make eye contact, not the user and the stand.
Something I didn't mention in the description, it would need to be bare eye contact. If the target is wearing something to cover their eyes, such as glasses (with lenses of course), or was behind a solid object, the ability would not activate.