100m coins.

It's pure PoS, so yes, all 100m coins are "premined".

Because the distribution of coins hasn't begun yet.

1. Block reward, same as in NXT (as Elastic was built upon NXT opensource code), depends on how much transactions this block contains. The more transactions it has the more fees from these transactions you get (fees are probably fixed at 1 XEL just like in NXT, though it can be manually changed by those who send transactions if they wish). Also the bigger your balance is the more blocks you forge (it's called forging, not mining).

2. But you can mine coins as well. And it's not same mining as in many other altcoins, but more precisely term would be "solving tasks" submitted to the network (this is a decentralized computer, remember?). So let's say a client submits his task he wants to be solved to the network, he puts a reward for it. And all nodes-participants (or supernodes only?) begin to solve small parts of this task. Some may have bigger parts to be solved then the others. When they finish their work, they submit results back to the client and receive some part of their reward depending on the contribution.

P.S. part 1 and 2 is just my opinion about how the system works and it may be completely misleading