I've dusted off the Phat launch PS3 and as I see the scene has moved on quite considerably. I just had a few questions if you guys would be so Kind...
I have a BC 60GB CECHC03 PS3 which is on Rogero CFW 4.55 V1.00, previously on some version of Rebug.
Q1 I there anything I need to consider with regards to updating or can I just go ahead and jump to CFW 4.90 Evilnat Cobra 8.4 [CEX]?
Q2 How does the Cobra 8.4 feature gel with the backward compatability offer by my console, are there any issues?
Q3 Lastly, and related to another CECHC03 40GB Console on 4.66 OFW... The console is fine apart from the BD drive not registering disks. Does CFW 4.90 Evilnat Cobra 8.4 [CEX] [noBD] basically remove the need for a disk to be in the drive inorder for the games to launch.
I only ask because my 60GB console needs a disk in the bay to launch content, have things progressed now?
Thank you for your time guys
Q1: You should be able to just go directly to Evilnat 4.90. Since you're already on CFW there's no need to jailbreak again, just install through system update via USB. If for some reason the update fails you can try updating gradually.
Q2: No issues. On BC models it'll use the available hardware (GS only in the case of CECHC) to provide the same level of backwards compatibility as OFW, for both original discs and backups. Please mind however that PS2 ISOs cannot be played from external USB disks or the network - they can only be played from the internal HDD or physical discs.
Q3: The broken Blu-Ray drive could be a serious issue. Basically it depends on whether the malfunctioning hardware is the Blu-Ray drive itself or the daughterboard. If it's the disc drive itself it's not a serious issue, you can jailbreak it and you don't even need noBD CFW (which is a big plus because iirc noBD breaks backwards compatibility). The main issue is if the broken hardware is the daughterboard, in which case only noBD firmware can be installed - attempting to install a non-noBD firmware will result in the console entering an update loop which cannot be aborted, basically resulting in a brick. Now the serious problem is that you can't directly install the noBD firmware in your case, since you're on firmware 4.66 - it's above 3.55, which means you can't install CFW without a jailbreak, and the jailbreak tool (bgtoolset) only supports versions 4.75 and above. For most people we just tell them to update to a supported OFW first then run bgtoolset, but since OFW has no noBD variant, well, you see the problem.
Basically you have three choices here:
1. You can see whether bguerville would benevolent enough to add support for OFW 4.66 to his toolset. He doesn't have a lot of free time these days so I wouldn't count on it, but if he does then that solves your problem because you could install the noBD CFW without having to go through another non-noBD OFW first.
2. You can take your chances of the issue being the Blu-Ray drive itself and not the daughterboard and attempt to install an OFW supported by the existing bgtoolset then jailbreak and install CFW. I can't tell you you'll be 100% safe but if the drive is unable to read discs but is able to digest / eject / spin them then the issue is more likely to be with the drive and not the daughterboard, allowing you to use non-noBD firmware. I'm not 100% sure though so don't blame me if it breaks.
3. You can decide not to take any chances and just keep it as it is. The problem here is that without being able to play discs and without being able to connect to PSN (which requires you to be on the latest firmware version) the only uses you have for the console is to play whatever digital games you already have installed on it and to play music / videos from USB disks.
Regarding your other questions -
As aldostools said, you don't need any separate app anymore. Evilnat's CFW already has both the QA flag toggle and the ERK dump functions already baked into the CFW, in the "★Custom Firmware Tools" menu under the network tab in XMB.
The QA flag is used to allow downgrading the firmware and also gives you access to the "★Debug Settings" menu option. It's not super useful in your day-to-day use but since turning it on has no drawbacks whatsoever most people just turn it on and keep it that way.
Dump the ERK then copy it to your computer and backup it safely so you don't lose it (cloud drives e.g., Google Drive, OneDrive etc. are recommended). The ERK is extremely useful because if your PS3 suddenly dies on you you can use it to read its HDD on your computer so you don't lose any games / game saves etc.
Just two more 
