In order to use this app your Shopify store plan must include access to the Carrier Calculated Shipping API
Yes, this app requires the Shopify Carrier Service API feature. It's included in your plan if you are on Shopify Advanced or Shopify Pro plans. If you are on the Shopify plan, it's free with annual plans or $20 on monthly plans — contact Shopify to add Carrier Service API for you. If you are on Shopify Starter or Basic plan, you will need to upgrade your plan to use this app.
Yes indeed! Try Zapiet - Rates by Distance for Shopify free for 30 days, so you can check how the app suits your workflow and does what you need. Cancel within that time, and you won’t be charged.
The app works everywhere that Shopify does.