2. Buy the PIC from me (later) or buy a PICKit3.
Do I really need the flashing as a user? I mean, will it work, if I just assemble the board and try to connect it via USB?
3. but for users they just need to know how to put 2 boards side by side and slide the connector on.
So for users your i2c will allow us to connect few boards (placed one-by-one and connected by wires) into one USB miner?
Then how many K16 boards can we combine? What wires do we need to connect the boards?
1) Yes. A new chip from Mouser or Digikey (or others) won't have Bkk's code on it, so how will it possibly interface with the ASIC chips? If you don't want to flash it yourself then you should wait for Bkk to announce sales of flashed chips. If you are buying a completed board from a vendor then they should handle the flashing for you and it will "just work".
2) Yes. The boards have the capability of linking together and using only one USB connection. I cannot tell you the max amount but the general idea is that the "slave" boards will communicate their results to the host through the "master" board that the USB cable is plugged into. There won't be any wires involved, there will be connectors on the edges of the boards that will plug into each other. Although if you wanted wires instead of a connector I suppose that would work too.