Re: Is it possible to get gpa for semester for the uni you studied overseas on exchan
I think you get one GPA per institution.
So using your example of Princeton, you would get an official transcript when you left to use when you returned home. This transcript would contain a GPA from Princeton, and the 4 subjects you successfully/unsuccessfully completed there.
When you return home (ie. to UNSW), you can apply for credit for these subjects to count towards your electives (or equivalent subjects if they exist). On your UNSW transcript, you will have a GPA for everything you have completed while at UNSW, and those 4 subjects you did at Princeton show up as their UNSW counterparts, with "credit granted"/ "exemption granted" or something similar. The GPA from Princeton doesn't affect your UNSW GPA, but the completion of the Princeton subjects does count towards you completing your UNSW degree.
Of course when applying for jobs and the like you can take each of your transcripts to show what you achieved at both institutions, but they would probably only really care about your UNSW GPA as that is where you attained your degree.
Hopefully that makes sense, as I think this is one of the least ridiculous questions you've ever asked on this site.