Hey @Nhan_Tran -
Those clauses cover a few different things. The order-sync requirement applies when a third-party-platform order is otherwise permitted under the API terms. It doesn’t authorize an alternative checkout by itself. Shopify’s express written authorization is still required before using another checkout or registering those transactions through the API if that makes sense.
Right now, there isn’t a public exception form or guaranteed approval path. For your public app though, I would reply through the existing App Review case or contact Partner Support with your app ID and submission reference: help.shopify.com
The same checkout restriction applies to custom apps, and custom distribution can’t be used across unrelated merchants. There’s a bit more info on this here: Do Custom Apps violating offsite checkout rules risk getting banned?
Let me know if I can help out further here - happy to clarify!