Problems About Curves in UE4.26

1.Why it cann’t live update the value of a curve,when using a curve in material system?
Here is my curve, when I changed the values, the material cann’t update the new values.
I saved the curve,and enable live update and live nodes,and also alpplyed the material.
But it doesn’t work.

And a net friend suggest I should change the value here, and turn the value back, then save the curve, and I did it! Then it worked . But why?

2.Why the curve cann’t read the value beyond 0- 1 second?, like 0-4sceonds?
I made a curve between 0 -4 seconds,
but in material, only the values between 0-1 went into effect,
I counldn’t get the values beyond 0-1 , that’s weird ,too.