It's a 2 MB flash device. It's obsolete and likely not supportable with any current firmware from OpenWRT or any other vendor (including TP-Link).
“VxKiller” is a heavily stripped OpenWrt Backfire 10.03 with MicroRedboot bootloader adapted for 2MiB flash and 16MiB RAM. There is
- no working DHCP server
- no wireless driver
- no WebUI
- no SSH daemon
- no writable RootFS
on this image. Its only purpose is to fit into the specs that the TP-Link's web interfaces accepts.
Even the "VxKiller" firmware, now nearly a decade old, didn't appear to provide much functionality. Installing "Backfire", or any version of OpenWRT that is not currently patched against vulnerabilities in the kernel, application firmware, wireless protocols,... and actively maintained is highly discouraged for any device, especially those that are exposed to the Internet in any way. (versions 17 and 18 are "current" in August, 2018)
Affordable, current "replacements" can be had for on the order of US$20. See, for example, the long thread of options and opinions: