Ensure all the partition boxes (Preloader, Recovery, Boot, System, etc.) are checked in the file list.
Flashing clean stock firmware completely overwrites your internal memory block. Treat these prep steps as mandatory: premio s87 firmware link
Install the Spreadtrum (SPD) USB drivers on your computer so it can recognize the phone. Ensure all the partition boxes (Preloader, Recovery, Boot,
Complete Guide to Premio S87 Firmware Link: Download and Installation Premio S87 Complete Guide to Premio S87 Firmware Link: Download
Before flashing, ensure your device matches these hardware specs to avoid using the wrong version, which could permanently damage your phone: : Originally Android 9.0 Pie. Memory : 1GB (1000 MB) RAM. SIM : Supports 2 Nano SIMs. Display : 6.0-inch LCD IPS screen. How to Install the Firmware
It is important to note that Premio Inc. does host firmware binaries on public open directories (like MediaFire or Google Drive). This is a security measure to prevent users from flashing incorrect BIOS versions, which can permanently "brick" the device.