Deployment of free enterprise apps in VPP

I've read a lot about the B2B iOS apps distribution, VPP program, however I'd like to be able to verify my knowledge and hope you could help. Let's suppose a company A develops an iOS application, publishes it to the Appstore as a B2B app (hidden for all normal users in Appstore), and adds a company B already enrolled in the VPP program to the list of entities eligible to buy the app. Furthermore, let's assume the app is free. What's the easiest way for company B to install this free app on their devices? The [document](http://images.apple.com/business/docs/VPP_Business_Guide.pdf) states there are two ways (MDM and redeemable codes), however [this page](https://simplemdm.com/2016/03/21/how-to-deploy-ios-apps-for-businesses/) mentions that B2B apps can be distributed with MDM only, and yet another source I've found stated that only paid apps can be distributed with both MDM and redeemable codes (the free ones are MDM only). So what is and what is not possible here? Can free apps be distributed by redeemable codes? I have several concerns: 1. Let's say a user within company B wants to install the app, using a redeemable code. How does he do that? Is it done by opening the App store, entering the code and the app will automatically become visible for that user (based on Apple ID)? 2. If yes, can users update the app through Appstore? 3. MDM can be problematic to set up, and I'm not sure why it's a better solution than redeemable codes (Apple deprecated codes for some reason). Also, I'm not aware of a free MDM (heard about Cisco's Meraki), not sure how free that thing really is. I'd be grateful if you could answer any of the questions above.