LabVIEW
Open file saved with 15.0 on another pc with 15.0
It's normal. Backsaving will save the VI as true 15.0.f0 version. Your installed LabVIEW version is either LabVIEW 15 SP1 which technically is 15.1 or at least 15.0.f>0 (the number after f being the bugfix version). So technically your installed LabVIEW version is almost always newer than the version it was last saved in after a backsaving.
If LabVIEW would save it as anything later than 15.0.f0 there is a chance that someone who still has the original release of LabVIEW 15 could not open it, as the routine that opens a VI is very strict about opening later versions of a VI down to the major, minor, and build version with build version being development, alpha, beta and release.
A beta version of LabVIEW cannot open a release version VI, even if the version itself is the same.
And yes save for previous doesn't need to save the compiled object code as that will be almost always anyhow recreated by whatever LabVIEW version you use to open the VI. The size of the VI as created by save for previous should be similar to the size of a VI saved with the compiled code configured to be saved separately in the compile cache, rather than in the VI. I would not expect that a massive difference between different minor versions for other reasons than this, but between major versions you can certainly expect some serious differences due to new features being added and some optimizations to the compression of certain parts of the VI resources.
