If your Istar unit has a white label with "Made for Hikvision" or uses Hikvision's SADP tool, it is almost certainly Hikvision OEM firmware. If the interface looks blue and clunky, it may be a Dahua OEM.
There are two primary methods to obtain the latest software. Always exercise caution and use reliable sources to avoid malware or corrupted files. Istar Firmware Download
No. Video files on the hard drive remain intact. However, your configuration (network IP, motion detection zones, user passwords) will usually reset to defaults. Always back up your configuration before updating (System > Maintenance > Export Config). If your Istar unit has a white label