Yes, you can create a demo board and place the stones or upload an already existing .sgf to your library
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For a game in the library you should be able to either start a full review by pressing the big blue button, or simply place a stone you want to check and the interactive AI analysis should kick in and display an optimal answer.
From both the library game and/or a demo board you can select “fork game” from the right hand side slide out menu. That allows you to challenge any player (inluding a bot) to a game from the current position. Bots may reject the game depending on their settings, so either check them ahead whether they support the desired board size, or try a few…
Demo boards do not get reviewed by our AI, the only workaround would be to download the demo board as an .sgf and upload it to your library.
Let me know if you need more details or screenshots for any of those steps.