ST-E3_RT and Canon 1Dmk4

I recently purchased a Canon ST-E3-RT, and I have two questions about using it with my old 1Dmk4

1.
The ST-E3-RT manual says I should cut back the sync speed on the 1D4, and that there is NO high speed sync on the 1D4, but when I try the ST-E3-RT and a remote 600ex2 with the 1D4, it seems to work fine on the full sync speed, and also seems to work fine on high speed sync.

Is Canon just being conservative, or is there a problem I am not seeing??

2.
Is there any way to make the zoom on the 600ex2 work if the flash is being triggered remotely by the ST-E3-RT?
The flash will auto zoom with the lens if it is mounted on the camera, but I can't make the flash zoom work with the ST-E3-RT.

I searched the forum for this, but could not find an answer----

Thanks!!

Don