Yes, you can install Virtual SmartZone (vSZ) on VMware ESXi 5.x platform.
Yes, you will need RTU (right to use), AP license (to manage more than one), and Support entitlement for future software upgrades. This is outlined in the vSZ Quick Setup Guide:
https://ruckus-support.s3.amazonaws.com/private/documents/790/vsz-3-1-1-quick-setup-guide-20150629.p...Single and Multi-tennant refers to the number of administrative domains that can be managed,
each like an individual controller per customer.
The vSZ-E (essential) is a single-domain, single customer/site controller, while the vSZ-H (high
scale) allows management of multiple domains, like an ISP with many individual customers they
support or provide services to.
Yes, you can have one or more APs at different network locations, so long as you can reach the
vSZ controller, and open the necessary ports for management/firmware updates, etc.