For 1 and 2.
Configure as below. Add tegra124-spi-slave to the device tree.
Should be 1
open ssh terminal and start the spi slave first with following command
"./spidev_test -D /dev/spidev0.0 -s 150000 -n100 -g30 -p4 -z
In another terminal start the spi master with following command
“./spidev_test -D /dev/spidev3.1 -s 150000 -n100 -g30 -p4 -z”