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How to install Flappy Bird on old devices (or new) for dummies

Check for 32bit compatibility.
iPhones: https://iosref.com/ram-processor#:~:text=A7-,iPhone%205c,%E2%80%94,-iPad
iPads: https://iosref.com/ram-processor#:~:text=iPad%20(gen%204,A4
iPods: https://iosref.com/ram-processor#:~:text=A8-,iPod%20touch%20(gen%205),%E2%80%94,-Apple%20TV
You can go to Settings -> General -> About to see your model.
I don’t have 32-bit compatibility

If you don’t have 32-bit compatibility, that’s okay. Keep scrolling ‘till you see the section marked “32 bit”.

Update to the latest version of iOS for your device. Make sure it is 6.1.6, 7.1.2, 8.4.1, 9.3.5/9.3.6, or 10.3.4.

When finish the update, check to make sure it says Up to date.

Jailbreak! iOS 6.1.6, iOS 7.1.2, iOS 8.4.1, Tutorials for: iOS 9.3.5/9.3.6, iOS 10.3.4

AppSync Unified (allows us to get the app on there)

Add the cydia repo cydia.akemi.ai
Install 'AppSync Unified'
Download AppManager.

Install FlappyBird!

Download FlappyBird IPA. Download version 1.0.
Open AppManager
Plug in your iDevice
Click Install
Select the FlappyBird IPA
And you’re done!

64-bit

Download Sideloadly
Download Flappy Bird IPA File

Open up Sideloadly.
Connect your device to your computer and trust it in iTunes or Finder
Under Apple account type your apple ID email
Make sure you trusted your device and it shows up under iDevice
Drag your IPA file into the sideloadly window. You can also click on the large IPA icon and select it from your computer.
Click Start
If you are using an apple ID for the first time with sideloadly, it will ask to enter the password and verification code that you will receive on a trusted device.
Your password is encrypted and is only sent to apple, however, I recommend you use a spare or alternate apple ID.
Once your password was entered and your account was verified, the IPA will install on your device.
To launch the app, go to Settings > General > Profiles and Device Management for iOS 14 and below. VPN and Device Management for iOS 15 and up.
Select the apple ID you chose to sign the app and click it
Hit Trust
You can now launch the app from your home screen.
Enjoy!