How can I be certain all of my old data has been transferred

With iCloud Backup, your data is always secure, even if you lose your device or upgrade to a new one. iCloud automatically creates regular backups of your iPhone, iPad, or iPod touch, including:

• Device settings: This covers things like your Wi-Fi passwords, wallpapers, and accessibility preferences.
• App data: The progress you've made in games, your saved login information for social media apps, and any other data stored within the app itself (unless the app uses iCloud Drive for storage).
• Photos and videos: With iCloud Photos enabled, your entire photo and video library is securely stored in the cloud and synced across all your devices.

It's important to understand the difference between iCloud Backup and iCloud syncing:

• iCloud Backup: This is a complete snapshot of your device at a specific point in time. Backups are created periodically and can be used to restore your entire device to its previous state.
• iCloud Syncing: This feature keeps specific data types (like contacts, calendars, notes, and reminders) constantly updated across all your Apple devices. Any changes you make on one device will be automatically reflected on your others.

While iCloud Backup ensures your data is never truly lost, there might be a slight delay in seeing the latest changes reflected across all your devices due to the syncing process. This means you might not see something you just added immediately on another device. However, rest assured, the data will eventually sync and become available.

In summary, iCloud Backup offers a safe and reliable way to store and protect your important data. While there might be short syncing delays, you can be confident that no information will ever be permanently lost.