eBay does not make older versions of the app available for download. Unless you have a backup of your phone saved somewhere, i don't think you'll be able to access older versions of the app. With the amount of tech issues you'd encounter on an unsupported app, I wouldn't suggest it, either.
If you're unable to update the app to a newer version, it could be you're working on an outdated device which no longer supports current versions of the eBay app. If that's the case you'll have to access eBay through a browser on your phone/tablet.
You might run into some tech issues even using the website if your device is unsupported. Same will happen for other sites and apps, not just eBay.
Unfortunately tech ages pretty quickly and once a device is no longer supported, it's upgrade or lose function.
