The answer to 1. and 2. is: We have a POSWebService that allows third-party integration.
So an integration can be done via this POSWebService.
In there you found: The use of this web service by a 3rd party requires that the 3rd party signs a NDA, joins the MICROS Partner Program and pays the required fees for this.
There was a possibility to import master data via ASCII Enhanced interface for Revenue & Master Data in the past.
Each interface must generally be checked by a specification. POSWebservice enables integration as described above.
To point 3 there are different approaches. First of all, it has to be determined what the exact reason of the splitting is. If it's just about reporting and exporting to a back office system, I would do that through the cost centers Hirarchi. In this case, there is only one database and you can easily transfer goods between the different cost centers. This raises the question of whether it is a location or if there are several locations that are many miles away and are not in the same network. These can be connected via VPN or RDP.
When it comes to multi-client capability, this is not mapped in MC. This is not necessary because the differentiation of clients in the back office software is regulated. MC can provide information in the export, which client.
However, if the customer really needs separate systems, internal transfers are not possible. A workaround would be to create a supplier A in both slave DBs. In one system you post a return and in the other system a goods receipt. In the HQ this can be shown in the reporting as well as at the local databases on site.