Every djay version you purchased is available to you at any time. The procedure where you find older djay versions varies. It depends on where you have purchased your djay version in the past, the Apple App Store our directly from the Algoriddim website.
Purchased in the Apple App Store:
Older versions of djay are no longer purchasable in the Apple App Store. This is why you will not find them via the Apple App Store Search. You will still be able to download your version at any time in the Purchased section. Please see this detailed guide on how to redownload an application.
Purchased via the Algoriddim website:
Please download the demo of the according version right below and enter your activation key.
Note: Only the website version requires an activation key. For further information about the activation key please see this FAQ.