Q1: Watch this:
https://www.youtube.com/watch?v=fCd6B5HRaZ8
Q2: There is no requirement for your probes to be dsDNA. Why are you so interested in capturing both strands? They have exactly the same sequence right?
RNA-DNA is more stable "because thermodynamics". Im sure there is plenty of literature on the subject:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC342109/ And plenty more references here:
https://www.quora.com/Why-is-the-RNA...NA-DNA-pairing