VLC for Mobile: This is the best app for playing local video files. It supports almost every format and runs smoothly on older hardware.
Microsoft Office Suite: Older versions of Word, Excel, and PowerPoint can often be downloaded via the "Purchased" trick, making the iPad 3 or Mini 1 a decent portable typewriter.
Older iPads are still fantastic for note-taking and basic organization.
Google Drive: Essential for accessing your files, though performance may be sluggish.
To help you find specific versions or alternatives, let me know:
Evernote: A classic choice for syncing notes across devices; the legacy version for iOS 9 remains quite stable.
Candy Crush Saga: Still frequently supports older iOS versions.
What is your for the device (e.g., kids' games, e-reader, music station)?
Which you are using (e.g., iPad 2, iPhone 4S)?
Before downloading new apps, you must know the most important secret for older devices: the "Last Compatible Version" prompt. If you try to download an app directly from an iOS 9.3.5 device, the App Store may simply say it is "Not Compatible."