Possibly. I'm not sure if we tested that specific CAN transceiver.

You can pick any pin that is not otherwise used (e.g. by UART, flash); for TxD, you need a GPIO that is output-capable (any <= GPIO34)

Suggest you mail sales@espressif.com for that. Note that due to CNY (which has been extended a bit because of the coronavirus), it may be a while before you get a response.

Those files mostly get converted into documentation by Sphinx, which has blockdiag as a plugin. If you want to look at the result, you can just check out the online docs we have.

Not that I am aware.

You are right. The ESP32 does have a MPU, but it is somewhat limited and not supported in esp-idf at this moment.

Yes, you can.

Keep in mind that I don't know that much about the internals of the binary stuff of the esp8266 SDK (I've not worked with that chip for the last 3 years or so), but yes, as far as I'm aware it has XTOS in ROM and the SDK uses that.

Well, depending on where the file is and if you use CMake or the old make process, you may have to tell the build system your cpp file actually exists and needs to be compiled as well. If you failed to do that, you would get exactly this error.

Sorry, I'm not familiar enough with the Arduino webserver to comment on this... Also, moving this topic to the Arduino subforum, perhaps the people there know more.

Moving to Arduino subforum.