HI
there is no problem downgrading the MSP, but you then need port the code so it matches the new MSP (associated MSP in the IAR project, SPI functions etc.)
The PER test will not run on the Kickstart version as the code size exceeds the 4 k limit of the kickstart version, however if you have a full license version in 5.30, I can give you an old version of the PER test compatible for the 5.30 version of IAR.
We unfortunately do not have any licenses to distribute for IAR