Naming Coordination Complex

Question

I am having issues naming the following compounds..

1. [Cu(NH3)2(H2O)4]^2 . The oxidation number of copper is 2.

2.CrCl2(en)2. Oxidation of chromium is 2

3. K4[Pt(CO3)2F2]. oxidation of platinum is 2.

4.[Ni(H2O)3(CO)]SO4. The oxidation number of nickel is 2.

Answer 1

#2 is not correct