WhatsApp for Samsung Galaxy Grand Prime Pro

The Grand Prime Pro runs Android 5.1 Lollipop, which sits right at WhatsApp's minimum supported version (Android 5.0), so it still works for now but is among the first devices that will be cut off as WhatsApp raises that floor. Keep the app updated from the Play Store while it still installs, and back up your chats now via WhatsApp > Settings > Chats > Chat backup to Google Drive so you can restore on a newer phone if a future update refuses to run. See how others solved this on Reddit

If a Samsung account is already signed in on the phone, the easiest route is Find My Mobile: go to findmymobile.samsung.com on another device, sign in with that account, and use Unlock to clear the lock remotely. If no Samsung account is registered, you'll need a factory reset by holding Volume Up + Home + Power to enter recovery, then choosing Wipe data/factory reset. This erases everything, and on power-up the phone will ask you to verify a Google account that was previously signed in (FRP), so make sure you know those credentials first. See how others solved this on Reddit

With only 8GB of built-in storage, WhatsApp media is usually the biggest culprit. Go to WhatsApp > Settings > Storage and data > Manage storage and delete large videos and forwarded files, then turn off automatic saving under Settings > Storage and data > Media auto-download. It also helps to add a microSD card and move your camera photos to it, and to clear app caches in Settings > Application manager to free up space. See how others solved this on Reddit

It remains usable for calls, WhatsApp and light browsing, but with just 1GB of RAM and Android 5.1 it struggles with multitasking, apps reload when you switch between them, and newer versions of WhatsApp or banking apps may run sluggishly or stop receiving updates. If you keep it, disable bloat you never use in Settings > Application manager (open each app and tap Disable) and treat it as a secondary device rather than a daily driver for demanding apps. See how others solved this on Reddit

The Grand Prime Pro uses an entry-level quad-core chip with only 1GB of RAM, so it was always slower than later A and S models and slows further as apps grow heavier over the years. To keep it responsive, clear cached data in Settings > Storage > Cached data, clear individual app caches in Settings > Application manager, restart the phone every few days, and uninstall apps you rarely use. See how others solved this on Reddit