I have some genomic coordinates and I want to retrieve their RNA sequence especially the ones for reverse complement ones (since RNA sequence would not be strand specific). Where could I find such tool or package?
you can also go to the UCSC Table Browser (https://genome.ucsc.edu/cgi-bin/hgTables), upload your input file as a custom track ("add custom track" button), select your genome, choose "sequence" as output format, press "get output" and choose "mRNA" from the following menu. This would output your mRNA sequences in FASTA format.
See this thread for details: