Yeah, but cannabis is a plant and plants and animals are higher organisms I've never heard of a higher organism use RNA as sole genetic material. Some viruses use RNA, like HIV, it basically hijacks your cell and uses reverse transcriptase to convert it to DNA after infection.

Once you get outta the viruses most everything else uses DNA to produce mRNA to produce proteins. But RNA probably preceded DNA as you suggest. There are several forms of RNA (mRNA, tRNA, rRNA) and some act as enzymes and others act to translate the DNA code to make proteins.

Viruses and prions are candidates for precellular life. Some argue whether or not viruses even qualify as life forms since they need a host to propagate.