The Cfw I would use would be the newest rebug or rogero. I would go with rebug 4.41. With the newer firmwares you don't have to worry about patching the games to work with lower firmware. Don't worry about converting your ps3 to dex. With someone that is a noob you wi brick it. Your ps3 is cex or retail system and keep it that way.
You can go online but you will get banned at some time. You don't need to go into service mode on your ps3 unless you have to fix something or downgrade. Most people are talking about safe mode. That is where you hold your button into it beeps once and shuts off. And hold again into the ps3 beeps twice real fast. The power button is the on you hold. And yes you need multiman to play backups.
1. I went with Rebug 4.30.2 spoofed to 4.41, I went with Rebug as it was the most recommended and they are always the first to come out with any updates if Sony update the OFW.
2. Not really sure, the Rebug I installed was CEX as standard.
3. There is no 100% safe way to making sure your not banned, but basic rules are never play COD Black Ops 2 online, never load up MultiMAN when signed in to PSN, or any other apps. You can still be banned at any time, I got banned just for updating my trophies, I never played online.
4. I never went into factory mode, just put the CFW on a memory stick and installed.
5. Yes you will still need MultiMAN or Iris to load up your games.
Glad to see that you downgraded your PS3, now you just need to choose a CFW,consider the answers above i agree with both of them, as for my opinion i'm on Rogero 4.40 spoofed to 4.41,playing online DOA 5, Naruto Shipuuden... etc & staying away from COD series & some other games.
I recommend using Rebug 4.XX CFW. Toggle QA of course (it won't hurt). Rebug is similar to a DEX firmware type which also makes it a good choice. Never play homebrew while connected to the internet (PSN). You can use multiMAN STEALTH on PSN (not regular mM). DONT go into factory service mode (even if you have a flasher, its a pain, trust me).
multiMAN to play disc backups? Yes. Use mM stealth patch if you want to use psn at the same time. This makes it where Sony can't detect it
Treyarch team gave a warning about a Ban Hammer of COD Black Ops 2 & also if you play it online the game will freeze after that you will be reported to $ony & then you're BANNED.
Why it happened with COD?
1. Call of duty is an addictive game so almost everyone is addicted to the game.
2. Someone wanted to reach the top of the mountain in a blink of an eye so(He/She cheated)
3. Then online gamers reported that someone is Invincible.
4. Treyarch team started improving the game's security & enforcement policies.
5. Then the BANHAMMER started.