Originally posted by Nitreb
Yes, you can go through the game with the arrows, but that only replays the moves that were actually made. To try alternative lines, i.e. to "analyze", you need to use the analysis board, but it shows only the final position, not the positions you reach with the arrows. In other words, with the analysis board, you can currently only analyze starting from the last move made; I want to analyze prior positions in the game.
Try it for yourself.
The analysis board has two sections:
Game history allows you to scroll through the moves that were made
Game analysis allows you to see the results of your own moves using the previous and next position arrows
Using the Game history find the position you want to analyse. Now start moving pieces around on the board. Then use the Previous and Next position links in the Games analysis section to review the moves you've made.
Use the 'position x of n' to see which of the theoretical positions you're looking at at any moment. Note: if you use the arrows in the Game history section this count will be increased for each position viewed. If you know the move number from where you want to start the analysis use the scroll bar to find it and click on the move number.
Also worth noting that you can't branch your analysis - The position x of n count will be reset if you move a piece mid way through a sequence.
Clicking reset removes all the history of analysis moves and puts the board back to how you started (which will be the last position in the game).