Chess Computers

There are 10 questions
Where can I buy the retro software for my Revelation II?
Can I use Revelation II as a normal DGT e-Board?
Can I use the DGT Pi without a DGT e-Board?
Does DGT Centaur have an ELO rating?
When I play on DGT Centaur, can I see my progress from game to game?
Can I save my game on DGT Centaur?
Can I connect DGT Centaur to an external device?
How long can I play with DGT Centaur without charging?
Why is the bottom of DGT Centaur not covered?
Is it possible to update the DGT Pi software?