Hi Leonard
Recovering the MP02s from a lost password is pretty straightforward.
There are three separate recovery mechanisms available (Failsafe, UBoot and Serial), but in your case the simplest one is just to use OpenWrt Failsafe.
The VT Wiki page describing this is here:
Once you have the device in Failsafe mode you can run the "mount_root" command to mount the file system as-flashed, then run the 'passwd' command to set the password.
For the MR3020 devices, as with any new device with OEM firmware, the approach is to flash it initially with a stable OpenWrt 'factory' firmware image. This ensures that the device is initially flashed with a known good image, and that it will have the Failsafe mechanism available should anything go awry subsequently. You can flash from the firmware upgrade screen of the original TP Link firmware.
The stable OpenWrt BB image is here:
Once you have the OpenWrt firmware installed you can flash the SECN firmware using the firmware upgrade screen in the LuCI web interface which you can access at 192.168.1.1
When upgrading from OpenWrt to SECN, be ** CERTAIN** to clear the checkbox that retains the settings, otherwise you will have SECN firmware trying to run with OpenWrt settings. In the OpenWrt firmware upgrade page, this setting is enabled by default, so you have to clear the checkbox before proceeding.
Regards
Terry