Google Workspace Addon incompatibility between different Workspace instances?

Question

I am developing a small Google Workspace Add on for a customer.

The way I am doing this is by developing it on a different Google Workspace and after testing, I copy it to the customer Google Workspace. However I encounter that there are some differences between those Google Workspaces because I got an error on the customer Workspace when using the Add on. The following piece of code worked on my Google Workspace:

 if(e.commonEventObject.formInputs && e.commonEventObject.formInputs.input){
     userSpeficiedIdentifier = e.commonEventObject.formInputs.input.stringInputs.value[0];
  }

However I received the following error on the customers Workspace:

TypeError: Can not read "value" of undefined. 

I was able to fix it on the customer side by adding [""] after input like this:

 if(e.commonEventObject.formInputs && e.commonEventObject.formInputs.input){
     userSpeficiedIdentifier = e.commonEventObject.formInputs.input[""].stringInputs.value[0];
  }

But this leaves me with some questions I can not answer:

1. What exactly is the difference between the customer and my Google Workspace?
2. How can I check before hand if such different in version exist and if there any compatibility issues?