Burn a rpd file on MAX10

I need to provide some interface to a user to download a rpd file into the chip.

So I some questions

What format of a rpd-file? byte-sized UTF-8 or may be some extended format like UTF-16?

I write with Avalon-MM - it ofers a single word 32-bit (4 bytes) write - so what endianess of a rpd file?

First I read all bytes

byte raw_data = File.ReadAllBytes(burn_file_path);

And then I send all bytes over a serial port

for (int i = 0; i < raw_data.Length; i+=4)
{
    word_to_write = (UInt32)((raw_data << 24) | (raw_data << 16) | (raw_data << 8) | raw_data);
    msg = WRITE_WORD + " " + word_to_write.ToString();  
    comport.Write(msg);
    progressBarBurnProgress.Value = i;
    response = ReadComPort(100, 10);
    if (response != ACK)
    {
        MessageBox.Show("Wrong response!");
        return;
    }
}

So the question is - this way

word_to_write = (UInt32)((raw_data << 24) | (raw_data << 16) | (raw_data << 8) | raw_data);

or this

word_to_write = (UInt32)((raw_data << 24) | (raw_data << 16) | (raw_data << 8) | raw_data[i);