What is the oxidation state of $Cr$ in $[Cr(NH_3)_4Cl_2]^{+}$?

The oxidation number of $Co$ in the complex ion $[(en)_2Co(\mu-NH_2)(\mu-OH)Co(en)_2]^{3+}$ is:

Which among the following is a correct formula of Barium tetrachlorocuprate$(II)$?

$A$ coordination compound with the formula $FeCl_3 \cdot 4NH_3$ has a coordination number of $6$ for the central metal ion. It does not lose $NH_3$ gas upon heating but gives a white precipitate with an aqueous solution of $AgNO_3$. What is the $IUPAC$ name of this complex?

The $IUPAC$ name of the coordination compound $[Co(NH_3)_4(H_2O)Br](NO_3)_2$ is:

The $IUPAC$ name of $[CoCl(NO_2)(en)_2]Cl$ is: