RE: Sense gate metal1 in pcell(lowest hierarchy) and draw metal1 path to connect all gates in a row of 10 pcells in current hierarchy(1 hierarchy above than the lowest hierarchy).

Often pcells have the ability to create structures like this themselves, by putting all the gates in a single nfet instance and turning on some parameter to connect the gates together. Consult your pcell documentation to see what features are available! Failing that, I think VCR or Virtuoso-GXL has some kind of fancy auto-routing feature that can do this.... Otherwise, you could code this up yourself with dbShapeQuery, dbGetHierPathTransform, dbTransformPoint/dbTranformBBox, and dbCreatePath.