Official VS 2015 received updates until October 2020 (mainstream) and extended support until October 2025. Pirated repacks freeze at a buggy RTM version.
Conclusion: Do not download a pre-made “portable” VS 2015. It is not worth the risk.
Microsoft never released an official portable version of Visual Studio 2015. Visual Studio is a deeply integrated development environment that relies on:
You cannot simply copy the Program Files\Microsoft Visual Studio 14.0 folder to a USB drive and expect it to work on another machine.
VS 2015 installs several services:
These require installation privileges and won’t run from a portable drive.