To get iTunes content on your iPhone, you don’t actually install iTunes on the device itself, since iTunes is a desktop app for Windows or Mac. Instead, you use iTunes on your computer to sync or transfer music, videos, apps, and other media to your iPhone. Here’s how: Install iTunes on your computer: Download the latest version from Apple’s website and install it. Connect your iPhone: Use a USB cable to connect your iPhone to the computer. Open iTunes and ensure your device is recognized. Sync content: In iTunes, select your iPhone icon. Navigate through the tabs like Music, Movies, TV Shows, or Books. Check the content you want to sync, then click Apply or Sync. Transfer purchases: To add items already purchased on the iPhone, go to File > Devices > Transfer Purchases from [your iPhone] in iTunes. Use iCloud alternatives: For wireless syncing, you can enable iCloud Music Library, iCloud Photos, or use Finder on Mac (macOS Catalina and later) to sync content without iTunes. Following these steps will get your iTunes media onto your iPhone efficiently, keeping your music, videos, and other purchases up to date.
you dont
If you are referring to an iTunes account, they can share. They do not need separate accounts.
Yes you need to activate it using Itunes, otherwise you wont be able to use it you will only see emergency calls only on the screen or a logo for USB cable pointing to an itunes logo. For the step by step procedure on how to activate iphone, just go the link http://nice-to-know-about-iphone.blogspot.com and look for the topic "Activating an Iphone"
you can, but only with an iTunes gift card
yes, it activates through iTunes. Which requires an Internet connection
Only if the iphone is a GSM phone with a SIM card... Otherwise if it is CDMA then no, you have to activate the other iphone.
Yes, restore it to factory settings by pluging it into iTunes first before taking it to AT&T
You can add a video on YouTube without going through iTunes on your iPhone by uploading it directly via your PC.
You can without but the easiest generally do use iTunes.
Im not sure but i think you have to jailbreak it
Itunes on the iPhone is preinstalled.