why can't i disable apps like email, internet, optical reader ?

Because there should be no reason you would need to disable them... They are core features of the phone

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Wait for things to settle down a bit, the root and install titanium backup. You can freeze unwanted apps.

I don't think there's a way to go back from a root attempt yet, so I'd wait a few weeks until you can install a custom recovery, return to stock etc. This'll all happen, but to the best of my knowlege, it hasn't yet. Until then, rooting is working without a safety net.