This puzzle was set with multiple solutions in mind. There are a total of 6 possible solutions to this one grid.
Killer Cage: All the given killer cages sum to the same total. Digits may not repeat in the cages.
Odd-Even : Grey circles are Odd digits, Grey squares are Even digits.
Thermos : Digits must strictly increase from the bulb end.
Arrow : Digits on the arrow must sum to the number in the circle.
Kropki : White dots show a difference of 1, Black dots a Ratio of 2.
Quadruple : Digits in the circle must appear in the adjacent blocks.
German Wispers : Adjacent digits along the marked blue lines have a difference of at least five.
Use the Cage total of 20 and the Odd-Even and Thermo clues.
Use the Cage total of 25 and the Odd-Even and Kropki clues.
Use the Cage total of 21 and the Thermo and Arrow clues.
Below is a grid with only the clues required shown
F-Puzzles link with only the required clues