First of all, all those surveys are FAKE. it is impossible to jailbreak your PS3 unless you are on firmware 3.55 or lower. to do so you have to downgrade it with an E3 flasher (this can only be done on the FAT and Slim models, not the super slim) You can either buy an E3 flasher (google it and how to use it) or you let someone downgrade/jailbreak it for you. and ofcourse you can also buy a jailbroken PS3 from ebay.
1) i think i answered that
2) True. Sony fixed it on all later firmwares but as I said you can jailbreak it on firmware 3.55 or lower
3) Memory stick is for placing the CFW (Custom Firmware) on. It's basically the update you install on 3.55 which gives you access to all the goodies

Not sure if you can use your external HDD tho
4) There's a chance that you might brick your PS3 while downgrading, also there's a risk of getting banned especially on newer games but there are a lot of ways to minimize that chance of getting banned. And if you ever get banned make a new account or buy/use a new CID (Console ID, every PS3 has a unique one, it's basically a line of numbers which Sony bans from their servers if you get console banned)
I hope this helps!