"ab" should work. "ab.tcz not found".
"tce-load" should work. However, repo.tinycorelinux.net returns 404 (using -wi flag to download and load on boot)
/tce should persist. I manually wget a tcz into /tce/optional/ and upon "sudo reboot", the directory was gone.
There is no such extension named ab.tcz, if you're looking an CLI app browser, try
tce-ab or
tce for short.
/tce is the tce directory for
cloud mode and is located in the RAM, therefore, application extensions are lost on reboot.
To set-up a persistent tce directory, type
tce-setdrive, but the TC should have already picked it up for you while it's booting.
As for the 404 error, check your network, if the problem persist, download
mirrors.tcz from a working computer and put it in your SD card.