Hey there, let's work through recovering your full SMS and iMessage history from that deactivated iPhone 4S. I’ve helped folks with this exact issue before, so here’s a breakdown of the most effective steps to try:

Since the iPhone 4S tops out at iOS 9, you’ll need an older version of iTunes to work with it—iTunes 12.6.5 is the last release that supports iOS 9 and below. Here’s what to do:

• Download and install iTunes 12.6.5 on your Windows or Mac (skip this if you already have it saved from back when you used the 4S).
• Connect your deactivated iPhone 4S to the computer, launch iTunes, and click the device icon when it appears.
• Go to the Summary tab, then click Restore Backup. Pick the backup file dated before your phone was deactivated—this is the one that’s most likely to contain your full SMS and iMessage history.
  • Quick heads-up: Restoring a backup will overwrite all current data on the 4S. If you’ve already recovered some conversations, export them first (take screenshots or use iTunes’ separate message backup option if available) to avoid losing them.

iOS 9 on the 4S supports iCloud sync for messages, so if you had this turned on before the phone was deactivated:

• First, you’ll need to get the 4S out of deactivation mode. If it’s locked due to too many passcode attempts, you’ll have to restore the iOS firmware first (using iTunes 12.6.5) and then activate it with your original Apple ID.
• Once activated, log into your Apple ID, go to Settings > iCloud > Messages, and toggle the switch on. Give it a few minutes—if your iCloud had the full message history saved, it should sync down to the device.
  • Note: If your iCloud storage was full back then, your messages might not have been synced. Double-check your iCloud storage history (via your Apple ID account page) to confirm.

If you don’t have a backup, some specialized iOS recovery tools can scan the 4S’s internal storage for leftover data. Look for tools that explicitly support iOS 9 and older devices:

• Install the tool on your computer, along with iTunes 12.6.5 (to get the necessary device drivers).
• Connect your 4S, select the SMS/iMessage scan option, and let the tool run its scan.
• Once done, preview the recoverable messages and choose to save them to your computer or restore them to the device.
  • Realistic note: Success here depends on whether the message data was overwritten. If the 4S was used heavily before deactivation, or if you’ve restored it multiple times, the odds go down—but it’s worth a shot for old, unoverwritten data.

• The 4S uses older NAND flash storage, which can degrade over time. If parts of the storage are worn out, some message data might be permanently lost and unrecoverable.
• iMessage is end-to-end encrypted, so if you don’t have a backup (local or iCloud), scanning the device directly might not retrieve encrypted iMessage content—stick to backup methods first for those.

内容的提问来源于stack exchange，提问作者jul