A game demo is a trial version of a video game that is limited to a certain time period or a point in progress. A game demo comes in forms such as shareware, demo disc, downloadable software, and tech demos.
Whether you're playing real casino games or free casino games, the RTPs (return to player percentages) are fixed. There is nothing that can be done to change the house edge in casino games. Casinos do not intentionally manipulate demo games to payout more frequently than real money casino games.