FR97 means that the record is not in chronological order in the original document. Instead of being among other records from the same time, it is on Frame 97 of the microfilmed version of the document.
As for whether it is the correct baptism, it could well be. However it is important to understand that in Scotland a wife does not legally change her surname on marriage. She retains her maiden name, even now, in legal documents, being recorded as 'xxx yyy or zzz' where 'xxx' is her given name, 'yyy' her own maiden name and 'zzz' her husband's surname. In the early 19th century she would usually have been known by her own surname. In the census it's quite usual for a wife to be listed under her maiden name, with husband and children bearing his name.
So in the baptism records it is her maiden surname that is recorded. Sometimes it is even spelled out; for instance I have seen several baptisms of children to 'Alexander Leslie and Mrs Anne Duff his spouse' in the 18th century records. If the mother's surname is the same as the father's it invariably means that it is also her own maiden surname.
There are nine baptisms of children to Walter Ross and Catherine Ross in Rosskeen between 1813 and 1842. However there are two marriages of a Walter Ross to a Catherine Ross in Rosskeen, one in 1813 and the other in 1836, and there is a gap in the baptisms between 1825 and 1837. So the nine children are not all the same family.
Therefore these Catherines' maiden surname is indeed Ross, not MacKenzie. It is possible that one record might get the mother's surname wrong, but not nine. It's far more likely that Janet Ross or MacLeod's mother's surname is wrong in the much later Australian records - it's quite common for a grandchild not to know the maiden surname of its grandmother, especially when the grandchild never knew the grandmother.
