While Cuphead was originally an Xbox console exclusive, it eventually made its way to the Nintendo Switch and, surprisingly, the Netflix Games platform for Android users. The version 1.7.0 APK usually refers to the cracked or extracted version of the Netflix release that includes the DLC content fully unlocked.
You are not out of luck. You can legally play Cuphead: The Delicious Last Course on your Android phone right now. Here is how:
If you are downloading the solely for the base game, you are missing out on a massive chunk of content. The Delicious Last Course (TDLC) is not just a few extra levels; it is a love letter to the fans.
In short, a stable, feature-complete that works offline does not exist from legitimate sources.