Product discounts also do not support ‘ALL’

We have a requirement to use local images on the product. Due to the high demand, we would like to upload product images using the rest amdin API, but I don't know how to generate "attachment" data. 

I also have such doubts.

I am using the discount function API to reduce different prices for different products, but only one product is displayed on the shopping cart or checkout with a discount price applied, and other products are not effective.I think the corresponding D...