Check current software: open Settings → About phone → Software information and note Build number, Baseband version and Security patch level. Use Settings → System updates (over Wi‑Fi) to fetch the official package. Back up contacts, photos and a full system backup to external storage or cloud before any upgrade. Official update path: download the firmware that exactly matches your model code from the manufacturer's support portal, verify the file's SHA256 checksum, then apply via Settings → Loc...