SM-T285 has a Spreadtrum (Unisoc) SC8830 chipset. It is not the same as SM-T280 (Wi-Fi only, Marvell chip). ROMs are not interchangeable . Flashing wrong firmware = hard brick. This process trips KNOX permanently and voids warranty.
The installation process may vary depending on the chosen ROM. However, the general steps are: sm t285 custom rom android 7 free