See Release Notes

• Bug fixes for general core bugs in 4.0.x will end 8 May 2023 (12 months).
• Bug fixes for security issues in 4.0.x will end 13 November 2023 (18 months).
• PHP version: minimum PHP 7.3.0 Note: the minimum PHP version has increased since Moodle 3.10. PHP 7.4.x is also supported.

• Moodle 4.0 Database Schema (by Marcus Green)