can i upgrade from 2.0 to 2.2 and use turbosim that cater for 2.2 after i upgrade. am i able to use all function and is the setting will be exactly like original 2.2?

Why dont you use Yellowsn0w? Restore to 2.2 (not 2.2.1!!), then use Yellowsn0w or get a custom firmware 2.2.1 (made with PwnageTool 2.2.5) and update from 2.2 to 2.2.1 then. 2.2-basband will stay and you can use Yellowsn0w.

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iPhone 3GS factory unlocked (3.1.2; Blackra1n, Cydia, OpenSSH, custom 3.0 ipcc file (no sig), tethering hack by Dev team, 32 GB)
iPhone 3G (3.0.1; Redsn0w 0.8, Cydia, OpenSSH) 16 GB