"Is it correct that the 747 leading-edge has krueger flaps inboard and variable camber leading-edge flaps (VCLEF) outboard?"
Yes.
"If so do the VCLEF's have a slot in their design?"
Yes, a small slot. Krugers do not.
"Is it so that the root stalls before the tip..."
I've been told that this is the case, but ... I'll leave this to the experts.
Regards.
NSEU