Apple manager MDM system

You can use Profile Manager, but even Apple themselves uses a third party MDM.

To deploy apps on your Apple devices, you don't necessarily need an MDM solution. Only registering your device on ABM can suffice and you can distribute apps using Apple VPP. This is ideal, especially if you have only a small number of Apple devices. However, if you plan to expand your Apple device inventory, MDM will give you more power and control that is beyond app distribution- you can control updates, performance, data usage and more.

Not from the general App Store. You must purchase from the volume store to deploy en mass.