On the Inverse Kinematics panel of the Preference Settings dialog, you set options for both applied and interactive inverse kinematics.
To prevent transforming unlinked objects while working in IK mode:
Single, unlinked objects are hierarchies of one object. An unlinked object is its own root and also a child of the world, so turning off Always Transform Children Of The World prevents you from transforming single objects in IK mode.
Applied IK and Interactive IK groups
The threshold and iterations settings are a trade-off between accuracy and speed. With the two groups of settings you can individually tune the behavior of Interactive IK and Applied IK. Interactive IK provides fast, real-time response, so you should set Interactive IK preferences for speed. Applied IK provides the IK solution to match the follow objects very closely. You should set applied IK preferences for accuracy.
Compares the second derivative of the end effector to a very small threshold. If the derivative is within the threshold, IK is terminated.
Applies in both move and rotate modes when IK is on. It affects only an object that is a direct child of the world when the object is selected.
For example, if the root of an IK chain is a child of the world, and you're manipulating an object at the end of the chain (the root object itself isn't selected), 3ds Max observes any constraints set for the root object. However, if you select the root object and try to move it, its constraints will be ignored.