What happens to the oxygen-hemoglobin $(O_2-Hb)$ dissociation curve when the temperature decreases?

With reference to the oxyhaemoglobin dissociation curve,select the $INCORRECT$ statement/statements.
$I$. $100\%$ saturation is very common.
$II$. $95-97\%$ saturation takes place at $ppO_2 = 100 \text{ mm Hg}$ in alveoli.
$III$. At $30 \text{ mm Hg}$ of $ppO_2$,only $50\%$ saturation can be maintained.
$IV$. The oxyhaemoglobin dissociation curve is $J$-shaped.
Select the correct option.

Oxygen dissociation curve shifts towards left due to increase in . . . . . . during internal respiration.

$CO_2$ is carried by haemoglobin as carbamino haemoglobin. This binding of $CO_2$ with $Hb$ is related to the partial pressure of .........

Identify enzymes $A$ and $B.$
$CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons HCO_3^- + H^+$

Identify $A$ and $B$ in the given oxygen-haemoglobin dissociation curve and choose the correct option accordingly.