Positions (i) and (ii) show the same die. In position (iii) it shows 6 on top and 5 on the left face. Which number is on the right face marked '?'

Read each corner as top → left → right. (i) gives 5 → 1 → 2 and (ii) gives 3 → 5 → 6, i.e. 5 → 6 → 3, so going round face 5 the neighbours come in the order 1, 2, 6, 3. (iii) reads 6 → 5 → ?, i.e. 5 → ? → 6, so ? is the face just before 6 in that ring: 2.