This speaks to the core appeal of the Naruto Senki Legends phenomenon: Modern mobile gaming is predicated on the "timer"—waiting for energy to refill, waiting for chests to unlock. The modding community behind Senki Legends rejected this capitalist architecture. Version 1.09 was often sought after because it represented the "Gold" or "Unlimited Money" standard. It allowed players to bypass the tedious progression systems and immediately access the fantasy of being the strongest ninja. It was a rebellion against the "Games as a Service" model, offering instead "Games as a Sandbox."
Go to your phone Settings > Security and allow installations from outside the Play Store. Install: Open the downloaded file and click install.