Thanks for your reply.
1) Do you know why I have kStatus_SDMMC_SwitchBusTimingFailed error with USDHC2?
-- I think it's related to the switch voltage sequence, whether you can tell the what response of the SD_SwitchVoltage(card) function.
Thank you for your interest in NXP Semiconductor products and
for the opportunity to serve you.
After having a brief review of the code, I've not found any errors in them.
So I suspect that it may be related to the hardware circuit, I'd highly recommend you to modify the sdcard_polling or sdcard_interrupt to test the USDHC2, as software architecture of these demo projects is more simple and close to the hardware layer, please give a try.