I have 28 APA-102 strips, 65 led each, that can't be chained together.

I have 28 APA-102 strips, 65 led each, that can’t be chained together. I’m using teensy 3.1. can I plug a strip on every pin pair on teensy 3.1, chain multiple teensy together and deploy a video wall with them, using fastled? Does it have this function ? I couldn’t find it in the wiki

You could plug a strip onto every pin pair - though many of the pairings would be using bit-banging to write out led data, not the hardware SPI ports - please see this page - https://github.com/FastLED/FastLED/wiki/SPI-Hardware-or-Bit-banging - for more discussion on hardware vs. software SPI output in FastLED.

As far as chaining teensy’s and using them to build a video wall - FastLED is primarily focused at LED projects where the bulk of the rendering work is done on the MCU itself. While FastLED can be used for video wall/video display like applications, there’s not a lot of tuning in it for that, so most of the software around it (regarding synchronization, chaining, etc…) you’ll have to write yourself.

If you were using WS2812’s, I’d recommend that you consider using Fadecandy boards for building a video wall. https://hackaday.io/project/3-fled might have some direction to look at using a beaglebone black as the driver for your project.