Value change: Euler to Quaternion then back to Euler

Questions
1

https://playground.babylonjs.com/#1ST43U#665
I have an euler rotation. After I modify it, I translate euler into yprQuaternion2, then I translate yprQuaternion2 into euler2. Why euler and euler2 has different value?

    var euler = box.rotationQuaternion.toEulerAngles()
    console.log(euler)
    euler.x *= -1 
    euler.y += Math.PI*(180/180)
    euler.y += 2*(Math.PI-euler.y)
    euler.z = 0
    var yprQuaternion2 = BABYLON.Quaternion.RotationYawPitchRoll(euler.y, euler.x, euler.z);
    var euler2 = yprQuaternion2.toEulerAngles()
    console.log([euler.x,euler.y,euler.z])
    console.log(euler2)

image Three console.log give three different output. What happens lol

2

In the 2nd and the 3rd logs, euler and euler2 are probably the same angle but presented differently in values.

4.886921905584122 / (Math.PI * 2) * 360 = 280 degree.
-1.396263401595464 / (Math.PI * 2) * 360 = -80 degree.

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