German Whispers: Along green lines, adjacent digits must differ by at least 5.
Region Sum Lines: Along blue lines digits must have the same sum within each 3x3 region the line passes through.
f-puzzles: https://f-puzzles.com/?id=y3sc5yve
CTC: https://tinyurl.com/yujdes25
Solution code: Row 1 + Column 6 (18 digits)