Another point:
"The statement "If $G_k \simeq H_k$ then ..." suggests that you believe this to be a likely event"------ Definitely $G \simeq H \implies G_k \simeq H_k$ but the converse is not true, i.e. you can have $G_k = H_k^{\pi_k}$ where $\pi_k$ is not a factor of direct product $P$ where $G=H^P$. so I am aware that" even if you were lucky and they are isomorphic, this doesn't mean that this local isomorphism is induced by any global isomorphism."