I have several questions about tools, pricing, etc. None of the available labels match my question

[gstrasd]

I am building my own website and want to use Shopify for some backend services. For example, I'd like to use the Shopify API to track my customers, orders, products, etc. I am NOT actually building a site using Shopify.

My questions:

1. What tools and dashboards are available to me use in this manner?

2. The API documentation states it allows up to 40 requests per minute. This is horrendous. What am I not understanding? 

3. What are the different tiers of an API account?

4. What are the SLAs? Are the number of requests per minute different with different tiers?

5. What is the tier pricing? (I will be making REST calls - NOT GraphQL)

6. How much is everything going to cost me with using Shopify in this manner?

I cannot find answers to these questions anywhere.