Hi byeongjinkim,
Presumably, if you own a package that is qualified for the 150deg C, then you should not have issues with the operating temperature.
Nonetheless, in case you want to change the frequency you can do that at your own risk by changing the clock registers from {Toolbox install path}mctbx_9s12zvm\mctbx_s12zvm\src\c_library\clk_init.c file.
Even if changing frequency is not supported by default within the toolbox you can modify your instance and based on Chip Reference Manual you could change the value the registers exposed by cmpu_s12zvm_init() function to achieve your goals.
Hope this helps!
Daniel