In case you’re still wondering. This app can take all your subscriptions from lemm.ee and copy them to another instance. When you switch to that instance and go to your subscribed everything should be on the second instance.
This way you don’t have to subscribe manually on multiple instances. I believe blocks will be added as well.
This app would have done step 4 without you having to do it yourself.
As for why to switch instances. It’s a matter of preference. The example you gave is a good reason. Obviously if your instance closes you would have to move so it’s nice to have a backup just in case