Google states that personal developer accounts created after November 13, 2023 must run a closed test with at least 12 testers opted in continuously for the preceding 14 days before applying for production access.
Meeting that minimum makes you eligible to apply; it does not guarantee approval. The application also asks about your closed test, app or game, and production readiness.
Google recommends clear test instructions, broad feature coverage, a feedback channel, regular feedback review, and action on relevant findings. Its public guidance does not specify mandatory daily opens, session lengths, or a hidden engagement score.