Consider having an android .apk file. How can I know which cpu architectures (arm, intel or mips) are assumed as target device? I read an answer in this site which says look for lib folder if there is folder named x86 in it it supports intel cpu and so on, but no all apks has this folder formating.
APKs without native libraries can run on devices from any CPU architecture. Only the presence of native libraries (i.e. files under lib/) affect the ABI targeting of an app.