There are thirteen brain games. Three of them are free forever, with no cap on how often you play: Match & Go, Mini Sudoku, and Pattern Flow.
The other ten open with Essential.
The full lineup
Free: Match & Go, Mini Sudoku, Pattern Flow.
With Essential, also: Mahjong, Word Ladder, Number Neighbors, Story Sequence, Trivia Challenge, Market Memory, Detail Detective, Target Search, Category Collector, and Steady Hands Garden.
Why three rather than all of them
The three free games are not a teaser set. They cover different kinds of thinking on purpose - matching, logic, and pattern recognition - so somebody on the Free plan has a genuine daily habit available rather than one game they get bored of.
Two or three games a week is a nice rhythm. You do not need thirteen to get the benefit.
What a locked game looks like
You can see it in the lineup, with a note that it opens with Essential. Nothing pretends to be available and then stops you halfway through a round.
Scores and streaks
Every round of any game counts towards your ThriveScore, free or paid.
If you played the full set during a trial and then moved to Free, your scores and history stay. The games close; the record of having played them does not.