What is the numerical value of spin only magnetic moment of copper in $+2$ state?

Match the species in List-$I$ with their correct electronic configuration in List-$II$.

List-$I$	List-$II$
$(1) \ \text{Cr}$	$(A) \ [\text{Ar}] \ 3d^8 4s^0$
$(2) \ \text{Fe}^{2+}$	$(B) \ [\text{Ar}] \ 3d^{10} 4s^1$
$(3) \ \text{Ni}^{2+}$	$(C) \ [\text{Ar}] \ 3d^6 4s^0$
$(4) \ \text{Cu}$	$(D) \ [\text{Ar}] \ 3d^5 4s^1$
	$(E) \ [\text{Ar}] \ 3d^6 4s^2$

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ $Cu^{2+}$ in water is more stable than $Cu^{+}$.
Reason $(R):$ Enthalpy of hydration for $Cu^{2+}$ is much less than that of $Cu^{+}$.
In the light of the above statements,choose the correct answer from the options given below:

Arrange the following ions in the increasing order of their magnetic moments: $(i) \, V^{4+}$,$(ii) \, Mn^{4+}$,$(iii) \, Fe^{3+}$,$(iv) \, Ni^{2+}$. $[V = 23, Mn = 25, Fe = 26, Ni = 28]$

Which of the following is a correct statement?

The $3d-$ metal ions are paramagnetic in nature because