I checked the documentation on http://tessel.github.io/t2-start/ and it says that:
Tessel currently supports the Long Term Support (LTS) version of Node.js.
As of today (https://github.com/nodejs/LTS#lts-schedule) there are multiple LTS versions of Node.js (v4.x & v6.x), so does Tessel 2 supports all of them?