Before I decide to get electric imp for myself, is there a possibility to play with its emulation? Then I could create one or more virtual instances in my account, deploy software on them, manually feed and read their input and output signals on screen.
no
I think there is a very simple reason to make no sense to have an emulator: no emulators will be able to give you even a small clue on how cool it can be in electric imp when you get it in hands.
Setup the information about WiFi, then get the thing online working, then start to put together the first tests.
With any platform, on emulator, this could be a piece of cake, like a 30 seconds job. Then you move to the real world and you start to find out that make for example an Arduino get on WiFi and start to do something for real it can take half a day. But with the imp it take the same 30 seconds of the emulator.
The thing that most impressed me the very first time I’ve done the blinkup of an imp it was the crazy fast time to get online over WiFi. We all have daily experiences with our gadgets get on WiFi. My Nexus Galaxy, my Note II, my iPad 3rd gen, they all take 10 to 20 seconds to join the WiFi in the office. The imp, in the same place, with the same conditions and environment, it takes less than 500ms… from power up and when decide to take it easy.
So there is no emulator that can offer you a feedback comparable to the real thing that you can grab with less than 40 bucks, including a breakout and shield board 
And if you go for an Hannah then you will have weeks of fun before start to think that’s time to “move to the next level”.
Enjoy!
Dimitri