Do not update via Sony’s network (XMB). Network updates will always install the absolute latest version, which may break compatibility temporarily. Instead:
Disable internet auto-settings. Go to Network Settings → Set DNS to manual: 8.8.8.8 (Google) or 1.1.1.1 (Cloudflare). Some ISPs block custom JS exploits. ps3xploit.com system update
You to reinstall anything on your PS3. The update is entirely server‑side. Do not update via Sony’s network (XMB)
Once the to OFW 4.90/4.91 is complete, you are ready for PS3Xploit. ps3xploit.com system update
The PS3Xploit team released tools that function as a "Software Flasher." This means if you are on a firmware version that supports the exploit, you can use the tool to "downgrade" your console's firmware capability by patching the core OS files (metldr).