Point out the incorrect statement regarding $Be$ (Group-$IIA$):

Which of the following compounds is obtained when carbon dioxide gas is bubbled through a slaked lime solution?

Choose the correct statements from the following:
$(I)$ In vapour phase $BeCl_2$ exists as a chlorobridged dimer.
$(II)$ $BeSO_4$ is readily soluble in water.
$(III)$ $BeO$ is completely basic in nature.
$(IV)$ $BeCO_3$ being unstable, is kept in an atmosphere of $CO_2$.
$(V)$ $BeCO_3$ is the least soluble among all the carbonates of group $2$ elements.

The setting of Plaster of Paris is:

From which of the following reactions can anhydrous $MgCl_2$ be prepared?

Beryllium and magnesium do not give colour to flame whereas other alkaline earth metals do so. Why?