Using Arduino header with DE10 Lite

Connecting Arduino seems to be easy, according to the user manual, yet I have few questions:

1) At power up, I assume both devices (the Uno and the FPGA) wake up with default IOs defined as input, correct? How to avoid collision between outputs until the FPGA and/or Uno are programmed?

2) What would be the best method to write an array of data from the Uno to the FPGA (about 2K of 8 bits)? A UAR$T can be implemented on the FPGA, yet perhaps to make the Uno generate write signal and data bus, same like a CPU would do?

3) Is there a sample code of Arduino programmed and it's relative FPGA Verilog, that demonstrated data transfer?