I think applying scale means changes the Object data dimensions and makes object scale to 1 but why its moving my armature?
No Animations attached and no delta transformations present also.
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It's because your armature has currently a pose, once you've applied the scale, go in Pose mode and reset the pose (AltR, AltS, AltG) and the armature will be back to its default position.
You've given your armature a pose, poses take the bones position in local space into account, if you apply the scale it changes the distances.