USB programming

Can the Imp005 be programmed via the host USB specified in the schematic connection?

No. The imp only accepts code over the secure TLS connection from the server.

Semi-unrelated: imps that support USB support this as host (ie they are like a PC, and you can connect USB devices to this port). You cannot connect the imp’s USB host to a PC’s USB host - a USB system has a single host and multiple slaves.