Thinking about building or catching up on what's new with the devs?
The QA Flag is a setting that is enabled when a console is in the Quality Assurance stage before it leaves the factory. It allows access to Debug Settings. It also allows downgrading to a lower version of firmware without use of downgrader firmware. It can be enabled with Rebug Toolbox or the qa_toggle package, or by enabling HEN.
A. Your PS3 must have the QA Flag enabled, which can be done with Rebug Toolbox, or by enabling HEN. From there, navigate to Settings → Network Settings and hover over the Network Settings icon. Press and hold
L2 + L1 + R1 + R2 + L3 + DPAD-Down. This will enable the Debug Settings section.
An Optical Drive Emulator is a device that allows you to run game backups and homebrew on a PS3, without requiring a jailbroken console or Custom Firmware (CFW). Depending on the brand, it may support more models than CFW and may run on the latest OFW. See this page for more information.
For PS1, a different emulator exists for discs and for PS1 Classic games from PSN.
For PS2, different iterations of hardware required different emulators and offsets. PS2 ISO launchers may have options to use a different emulator. In general, model-specific emulators have much better compatibility and performance, and the PS2 compatibility list is based on the ps2_netemu.
A. While this subreddit and Wiki is great for end-users, you are unlikely to find expert developer help here. You can see past and present research at the psdevwiki, and get live help on the following IRC channels: #psdevwiki, #ps3dev, #psl1ght. PSL1GHT is a community-made open source SDK used to develop homebrew.