I have came across a few genes that show different nucleotide sequence in different databases. I then found out that the sequences are actually reverse complement of each other. How do i determine which is the actual nucleotide sequence of a gene,and not the reverse complement version of it?
You run a blast of your sequence. Then explore the results and you'll see somewhere that says "strand" and is indication whether is plus/minus.
Also blast has a graphical interface in which you'll clearly see the matching and non-matching bases. Therefore it should help you to identify the differences between the 2 sequences.
In general, if you look up a transcript sequence it will be in the correct orientation. If you look up a gene based on genomic coordinates, it may not be.
We can't tell you why your first sequence is in the wrong orientation from what you pasted.