Is accept_odds_change mandatory?

This field is mandatory; it is based on the setting in your bet slip, where a user can potentially select if odds changes are automatically accepted or not during ticket placement (bet delay). If you don't have such an option in your bet slip, then this should always be set according to your business rules (usually “None”, meaning that the bet is not accepted if the odds change during the bet pending delay). Otherwise, it should be based on the player's bet slip options.