From what I can see you need the omnichannel from magespaceX which has all features you need .
Stay away from magespacex!
In June 2019 I bought their POS together with a customizing. I never received the customizing nor any feedback of their support - no reaction to any of my inquiries. They are basically "dead". I thought they are out of business, instead new products pop up - I guess it is just the ways they do business...just fraud.
Magespacex came to my attention after being promoted by Magestore and yes their WebPOS has been just buggy. Initially I bought their WebPOS that eventually after almost 6 month of bug fixing worked more or less in order to be compatible with M2.1.7 I bought their PWA POS I received a version that did not work at all! Updates were also not provided they suggested to buy their Omni-Channel Solution for $4000. Shame on them.
As per your request, I would recommend you to have Webkul's Magento 2 Point of Sale System that offers all your requested functions.
A complete Web-based POS solution for managing multiple physical stores, retail outlets at different locations, and sync data (sales, order, inventory, products) with an online store.
Cashiers can scan barcode labels, manage customers, take offline orders, give custom discounts, split payment (card swipe/cash), apply coupon/voucher code, cart-on-hold, print sale receipt.
Magento 2 POS system is a bridged solution for managing online and physical store inventories.
Hope this solution will be helpful, if not then you can contact the support team for further customization to make this extension fit for your purpose.
If you're still looking for a POS system, ConnectPOS will be a great choice. The team update the app frequently and the customer support is nice. You can have every needed feature to connect your online and offline store. And there's also a 14-days free trial to see whether or not it fits your business.