XmaX wrote:

If it is, then it adds a nice feature to travelling to DLR and other
stations without the barriers. I can just go to Canary Wharf shopping
centre, buy some stuff, and go back, paying just 1 quid (i live in
Z2). Is there anything that can go wrong in this method? Any exception
from entering and exiting at the same station etc.?

If you don't touch out and then back in again at Canary Wharf, you could
be done for fare evasion.

And last question - is there any website I can check what exact fare
would I be charged when travelling between two stations? On some
journeys there is a choice of going through Z1 or not, and I would
like to know which of these applies on the particular journey.

Yeah, it's on TfL's web site.
--
Michael Hoffman