This is a rooting hormone with the main ingredient being indole butyric acid.

Rooting gel is a hormone used for helping cuttings establish a root system.

Yes. You can clone a marijuana plant without rooting hormone, the rooting hormone simply helps encourage root growth following standard cloning procedure (see google) without using hormone will work, although this varies in success rate from strain to strain...

excretion

No. Rooting hormone only works on the cut surface of a cutting as it helps the cutting to callous and encourage the formation of root buds.