Flashing an F18

Personally, I use the nRF52DK just because the tools for it work well. As I understand it though if you're using OpenOCD you can you pretty much any device you want.

i can flash the slim st link v2 clone as a DAP?

Yes, for that get two (it is <$2 item after all) and flash one with another. But you can also buy DAP dongle directly, search aliexpress for "daplink". Just beware, the cheapest ones are based on WCH549 chip which is 8051 family and while it works it is quite slow, better get one with arm chip inside.

If you get that stlink V2 dongle I have a build of CMSIS-DAP that enables also UART over SWIM/RST pins. And BTW you can even run stripped down Espruino directly on stlink https://github.com/fanoush/EspruinoBoard­s/tree/master/STLINKV2

You can also use Raspberry Pico with picoprobe FW.

And BTW in theory you can now unlock nrf52 even with original stlink firmware, recently there was stlink-dap.cfgadded to openocd which exposes lower level DAP interface of stlink https://review.openocd.org/c/openocd/+/4­904/9/tcl/interface/stlink-dap.cfg so the commands for unlocking are there. For some reason it did nothing when I tried but it may work for you.

thx u guys for reply,
i have to digest it for sometime.

thanks