Which of the following compounds gives $N_2$ on heating?

Which of the following fluorides does not exist?

Ammonia can be dried by

Which of the following processes does not produce ammonia gas?

Based on the compounds of group $15$ elements,the correct statement$(s)$ is (are):
$(A)$ $Bi_2O_5$ is more basic than $N_2O_5$
$(B)$ $NF_3$ is more covalent than $BiF_3$
$(C)$ $PH_3$ boils at a lower temperature than $NH_3$
$(D)$ The $N-N$ single bond is stronger than the $P-P$ single bond

Which of the following is not known?