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I wonder what is its function and if it can be the genetic material for a living organism. If not, why?

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Yes, double-stranded, helical RNA exists. It can occur naturally, a famous example would be Rotavirus, as well as synthetically in the lab.

Please note, however, that viruses strictly speaking do not qualify as a living organism.

References:

RNA double helix structure identified using synchrotron - McGill University

Double-stranded RNA viruses - Wikipedia

Rotavirus - Wikipedia

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  • $\begingroup$ dsRNA can also occur in mitochondria, since they have circular genomes, both strands of which get transcribed. This can cause problems if the mitochondrial dsRNAs accumulate and leak out into the cytoplasm, since dsRNA is highly immunogenic: nature.com/articles/s41586-018-0363-0 $\endgroup$
    – timeskull
    Jun 22 at 17:05
  • $\begingroup$ Single-stranded RNA (like DNA) can also fold back on itself, creating base-paired helical regions, as in tRNA. It is thought plausible that originally RNA served as both the genetic material and as the structural material before DNA and proteins came about. $\endgroup$
    – Armand
    Jun 22 at 17:07
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As the OP asked for double-helices and did not mention dsRNA, I would like to point out a tool developed by my close colleagues, that predicts secondary structures of RNAs from sequence.

http://rna.tbi.univie.ac.at/cgi-bin/RNAWebSuite/RNAfold.cgi

Here, base-paired regions are assumed to be in helical conformation.

You will see that most RNA sequences have some theoretical potential for auto-base-pairing with small, albeit temporary, helices.

Further, you asked about function of helical RNAs, which I more generally interpret as "structured" RNAs: Important terms or examples that you can further research are: 1."Rybozymes", which are RNAs with enzymatic functions; "Aptamers", which are RNAs found or created by SELEX that can bind biomolecules and even inorganic compounds with high specificity; 3. RNAs that have important functions in "RNA-protein complexes" as found in the ribosome, splicosome, telomerases, nucleases, RNPs and more..

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