Crash Bandicoot 2: Cortex Strikes Back has 25 levels.
The game's main progression is organized through five Warp Rooms. Each Warp Room contains five standard levels, producing a total of 25 crystal-bearing levels.
Players advance by entering these stages, collecting their crystals, and reaching the end of each level. After completing the five stages in a Warp Room, Crash faces a boss before gaining access to the next area.
The game also includes boss encounters and secret content, which can cause some counts to appear higher when discussing every playable area or completion objective. However, the standard level count for the original game's main campaign is 25.
Therefore, 27 is not the canonical answer when the question asks how many levels the game has. The figure of 25 refers specifically to the main levels connected to the Warp Room progression.