a) I don't know if protein-folding software is good enough to figure out the exact structure of the resulting protein given just the gene, but I suspect you could figure out through the equivalent of the strings command - looking for sub-chains of the protein, and looking for matching sequences in the gene
b) Coronaviruses happen to be RNA viruses; that is, their genomes are RNA rather than DNA. DNA viruses also exist and are common. We got full genomes from sequencing early in the pandemic, and continue to use it to monitor the evolution of the virus (see e.g. [1], where the results are available for download). Sequencing is very cheap and easy these days - you take a sample from a patient, use chemicals to break down all the cell membranes and such, sequence all of the DNA and RNA in it, and look through the results for a virus genome (i.e. something that isn't a human chromosome and isn't a known virus or bacterial genome). "m"RNA is more a description of the function than the chemical - tRNA and rRNA are short snippets of RNA used for manufacturing purposes inside the cell, while mRNA is the long chunks that actually carry information from the DNA to the protein manufacturing sites. Virus RNA basically functions as imposter mRNA, getting those manufacturing systems to make more viruses.
b) Coronaviruses happen to be RNA viruses; that is, their genomes are RNA rather than DNA. DNA viruses also exist and are common. We got full genomes from sequencing early in the pandemic, and continue to use it to monitor the evolution of the virus (see e.g. [1], where the results are available for download). Sequencing is very cheap and easy these days - you take a sample from a patient, use chemicals to break down all the cell membranes and such, sequence all of the DNA and RNA in it, and look through the results for a virus genome (i.e. something that isn't a human chromosome and isn't a known virus or bacterial genome). "m"RNA is more a description of the function than the chemical - tRNA and rRNA are short snippets of RNA used for manufacturing purposes inside the cell, while mRNA is the long chunks that actually carry information from the DNA to the protein manufacturing sites. Virus RNA basically functions as imposter mRNA, getting those manufacturing systems to make more viruses.
[1] https://www.ncbi.nlm.nih.gov/datasets/coronavirus/genomes/ - SARS-CoV-2 is the COVID-19 virus. As of my fetch, there are 71,509 full sequences of the virus, reflecting slight mutations over time and space.