Step 1: Understand what the question is asking.
We are told four statements about hexagonal close packing (HCP) and we must find the one that is NOT correct. So let us check each one calmly against what we know about HCP.
Step 2: Check the coordination number.
In any close packing, whether HCP or CCP, each sphere touches $6$ neighbours in its own layer, $3$ above and $3$ below, giving a coordination number of $12$. So this statement is correct.
Step 3: Check the packing efficiency.
Both HCP and CCP are close-packed, so the spheres fill $74\%$ of the space and the empty space is $26\%$. This statement is also correct.
Step 4: Recall the stacking pattern of HCP.
HCP follows an ABAB type pattern. The third layer sits exactly above the first layer, not in a new position. A useful fact is that in HCP the spheres of the third layer sit over the octahedral voids, while it is in CCP (ABCABC pattern) that the third layer covers the tetrahedral voids.
Step 5: Test the doubtful statements.
The statement that the fourth layer aligns with the first layer is just the ABAB rule (A is layer 1 and 3, B is layer 2 and 4), so it is correct. But the statement that tetrahedral voids of the second layer are covered by the third layer describes CCP, not HCP. So that one is wrong for HCP.
Step 6: State the incorrect statement.
The statement that does not hold for HCP is the one about tetrahedral voids being covered by the third layer.
\[ \boxed{\text{Tetrahedral voids of the second layer are covered by the spheres of the third layer}} \]