A session is a set of actions executed on our browsers, which is equivalent to an API call. Sessions are not limited in time.
The number of browsers associated to your plan represent the concurrency limit.
Dashblock works with datacenter proxies but you can use your own proxy with one line of code.
Yes, when you start you have a one-off trial package including 100 sessions and 10 browsers.
Yes, unused sessions accumulate month over month as long as your plan is active.