My first core works fine on WebIDE and App
But second core have problems. I can’t make it work with with WebIDE.
Second core works only mobile app.
How do you make bootload on sparkcore?
First it would be good to find out why Web IDE doesn’t work.
Next, CLI would definetly be worth to get up and running on your machine.
The next thing would be using dfu-util.
And finally you could go the JTAG way - similar to your image above - via these pins
https://docs.particle.io/datasheets/core-datasheet/#jtag