Legal transactions for AXI FIXED mode

Hello,

I am currently using AXI with burst type of FIXED for writing into a fifo. its data bus width is 32 - bits.

1. So i wanted to know whether AWSIZE of 64-bits and greater are legal or no. If it is legal then how should the data be stored in the fifo space? Will the lower 32 bits be written first and then upper 32 overwriting the lower 32 bits? or just write the lower 32 bits and rest of the  data is discarded.

2. For AWLEN > 0, and the AWSIZE <= 2, is the data overwritten on the same space? So the last written data is seem in that space?

Thank you.