(vii) They have been building a wall since three days

Don't you think, We use "For" here ?

(vii) They have been building a wall for three days

(i) He swore on God
Correct:
(i) He swore by God

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كُلُّ نَفْسٍ ذَآئِقَةُ الْمَوْتِ - Every Soul Must Have The Taste Of Death