I also have some problem when I updated ionic / cordova and created my first application with ionic 3, after which I can not start my old application with ionic 1. Below are the steps that I took to start my application with ionic 1
1. Return to the newly created project (with Ionic 3. *) and open package.json
2. There should be a line like "@ ionic / cli-plugin-ionic-angular"
3.Copy this line for package.json of your Ionic v1 project (in the V2 application there may be other plugins starting with cli-plugin - .., and you can also move them)
4. Change ion angular to ion 1, like this "ion / cli-plug-ion"
5. Run npm install in the project folder v1
6. Register the ionic.project file in the ionic.config.json file
7. Then try ion flow
hope your v1 application will be launched