You can claim your device to your account by using an internet connected WiFi once, claim the device, disconnect from that WiFi network and use the device wherever you want.
Next as long you have a computer that has internet access, you can use any way of your liking to build.
In order to flash you need physical access to the device via USB and then use CLI or dfu_util.
The respective instructions can be found in the docs
https://docs.particle.io/reference/cli/#particle-flash
https://docs.particle.io/reference/cli/#particle-compile
https://docs.particle.io/guide/tools-and-features/cli/electron/#flashing-over-serial-for-the-electron (also applies to Photon)
If you haven’t you might want to install a local toolchain or use the alpha stage local compiler