It seems there might be some confusion. CactusVPN is a VPN service, but I do not recall it being available as a standalone APK file. Most VPNs either distribute their software through third-party apps or download as standalone files. If you are looking for a standalone VPN application, I recommend checking out popular VPNs like 6Days, 2Days, or Netnanny through their official websites or app stores. If you're looking for a custom VPN application or a specific one, you might need to download it from a developer or a developer network. However, always be cautious when downloading or using software from unknown sources, as it is often better to use well-known and trusted VPN services. Using a VPN requires an internet connection, and it's important to use it responsibly, especially in public places. If you're unsure about the authenticity of a particular VPN, it's always a good idea to verify its credibility through reviews or trusted third-party sources.