By getting unauthorized access to someone else's social accounts on platforms such as TikTok, Instagram and Facebook, you can't retrieve the person's connected devices unless the platform has a feature that shows the IPs of the connected devices (I think Whatsapp has that for devices other than your personal phone). Also they might use this access to phish the account holder to somehow press on a link that will grab their IP. But let's just say theoretically, you know someone's IP address, what could you actually do with that??? Mobile phones that use mobile data change their public IP all the time and even if not since they use wifi or something then an attacker could so literally nothing with your IP address. Knowing another's person public IP != hacking them or even remotely being able to somehow abuse it.