Install Keynote on a third generation ipad I have a third generation Ipad with ios 9.5.3.

In the app store I can try to buy Keynote.

Everytime I do that, the app store begin telling me that I need IOS 10.

Before IOS 10, how could people get keynote on a third generation ipad?

And now?
You should see a message to download the latest version compatible with your iOS version. At least that's how Apple handled these things in the past.

This may be a temporary bug.

Some Apple apps got updated a few days ago. Previously these apps worked just fine with iOS 9.2 or higher.