Yes. If you have administrator permission you can create all the users you want.
Yes. As indicated above, each Flame user will have a totally personalized experience, so that they will see specific locations, certain KPIs, etc. Likewise, you can create your custom dashboard or control panel.
In many cases yes. Flame is integrated with a large number of brands and devices. Especially WiFi. Depending on what you want to measure (queues, heat maps, influx, etc.) it will be necessary to study whether it can be used or not.