2 questions about Tobi's S/T

[Uxellius]

I've got 2 questions about Tobi's S/T mecanism:
The first is when tobi did this

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Minato's Kunai passed through Tobi's head and so Tobi's hand did with Minato's arm -which can only be explained by Tobi only can teleport his whole body at once- , and when Kakashi explained S/T lately he said something like

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Tobi's seen only teleporting his head so he was able to teleport only the targeted body part, my question's why didn't Tobi teleport his head and just let himself grab Minato at that moment?
The second Since Tobi intangibility & Teleportation are the same jutsu that take him to this dimension

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the dimension seems Dark and non-transparent How could he see Konan's Tons of paper bombs here:

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Answers're appreciated

 

[ShiroT]

maybe he can't activate the jutsu while touching objects and maybe its just dark to show that his face was existing somewhere else.