1. Does Caissa chess implement ​"en passant" rule ?

Yes Caissa chess implements it, as well as any other chess rule known to ​FIDE.
Please check ​our "en passant" demo on youtube.

2. What is the strength level of Caissa's chess engine ?

We estimate the engine is capable of rendering decisions at 1900-2000 ​ELO level. This engine was designed to perform on mobile platform, with power efficiency in mind. We are working on ​CM mode, which will make Caissa significantly stronger.

3. Do I have to pay for subsequent update ?