The docs recommend installing CLI on Mac/Linux with
bash <( curl -sL https://particle.io/install-cli )
So if you enter particle --version and a version number does not come up (the latest is 1.39.0), then do the bash thing. Afterward, see if the version # comes up correctly; if you do that, then you should be able to flash the 0.9.0 system-part1, Tinker, and bootloader to your device.
BTW flash system-part1 and Tinker via --usb (DFU) mode first, and then do the bootloader in --serial mode.
With device in DFU mode mode:
particle flash --usb system-part1-0.9.0-xenon.bin
particle flash --usb tinker-0.9.0-xenon.bin
With device in Listening mode:
particle flash --serial bootloader-0.9.0-xenon.bin