Yes i was able to play signed on my non-rooted phone. Thanks a lot. Apparently, i can just install it from scratch, not overwriting the playstore ver and work just fine. Probably the issues i'm facing is just like others said, some enemies can't OHKO'd.
I tried downloading and installing signed apk over the original, but it came up with an error saying that the package conflicts with an existing package by the same name. Do i need to root my phone?