The unitary subgroups of group algebras of a class of finite $2$-groups with derived subgroup of order $2$

Let $p$ be a prime and $F$ be a finite field of characteristic $p$. Suppose that $FG$ is the group algebra of the finite $p$-group $G$ over the field $F$. Let $V(FG)$ denote the group of normalized units in $FG$ and let $V_{\ast }(FG)$ denote the unitary subgroup of $V(FG)$. If $p$ is odd, then the order of $V_{\ast }(FG)$ is $\mathrm{\mid }F{\mathrm{\mid }}^{(\mathrm{\mid }G\mathrm{\mid }-1)\mathrm{/}2}$. However, the case when $p=2$ still is open. In this paper, the order of $V_{\ast }(FG)$ is computed when $G$ is a nonabelian $2$-group given by a central extension of the form $$1⟶{\mathbb{Z}}_{2^n}\times {\mathbb{Z}}_{2^m}⟶G⟶{\mathbb{Z}}_2\times \cdots \times {\mathbb{Z}}_2⟶1$$ and $G^{\mathrm{\prime }}\cong {\mathbb{Z}}_2$, $n,m\ge 1$. Further, a conjecture is confirmed, namely, the order of $V_{\ast }(FG)$ can be divisible by $\mathrm{\mid }F{\mathrm{\mid }}^{\frac{1}{2}(\mathrm{\mid }G\mathrm{\mid }+\mathrm{\mid }{\mathrm{\Omega }}_1(G)\mathrm{\mid })-1}$, where ${\mathrm{\Omega }}_1(G)=\{g\in G\mathrm{\mid }{g}^2=1\}$.