The demo has received a huge update to match the current state of art of the main game.
This was done because the old demo was too outdated including performance issues, bugs and glitches that will not representing well the actual state of the game.
The new demo is closer to the current game.
However, compared to the old demo, few things new were added but some others were removed such as the option to play the unlimited mode.
On the other hand, you can expect similar experience with limited amount of components, tools, task and also doesn't include a save/load system.