Can you jailbreak and iphone 3 to update past 4.2.1?

Can you jailbreak and iphone 3 to update past 4.2.1?

No.
you can jailbreak with whited00r 6 and get some ios 6 features like siri, reminders, etc but won't be able to get new apps.
whited00r comes with a app store with older versions of apps like facebook and alot more that will work on the i3

1. There's no iPhone 3. 3G or 3GS.
2.No. Nothing will update an iPhone 3G past 4.2.1.

IPhone 3G maxes at 4.2.1.
iPhone 3GS is updatable to 6.0.1.