No to the first, that's never been stated.
No to the second, Sasuke didn't get it because of that.
Not necessarily, what happened to Kakashi is still unexplained.
Not for the normal sharingan (when an Uchiha uses it).
the second is kinda true sasuke was hoping to save naruto right
and iam pretty sure that obito got his when he tried to save his companions
He tried to save Naruto after he got the sharingan, at first he was just focused on fighting (I just reread this recently actually).
Obito also tried to save his friends .i think if just there is abig will or wanting to save another person then it will be activated
obito failed 2
Btw if MS detoriates your normal sight only and detoriations doesnt count in sharingan mode then there is a plot hole.
How would kakashi know if MS detoriate his normal sight if he doesnt use his sharingan eye in normal life. His left eye is used only when he use sharingan so how the hell does he know if MS detoriates his lef eye normal sight if he doesnt use it. After all it cant detoriate his right eye if he doesnt use MS on his right eye. Plot hole for me ...
maybe its a much milder eye deterioration, and since kakashi cant switch off his sharingan he would know from the times he uses it,were as the clan can switch it on and off giving it more time to relax
i think Kakashi achieved the MS through the death of Obito. It just didn't activiate until he encountered Itachi. But then again I could be wrong.(Sorry for the shallow idea)
over use can give him eyesight defects like myopia,which might be evident even with the sharingan on.
or maybe tsunade could have detected kakshi's defect and informed him.
that isnt a plot hole.
i personally like to think that the great copy ninja kakashi copied itachi's MS when it was used on him too(or at lest recorded how itachi activates it and achieved it himself later on)