SAM-ICE supports all ARM based Atmel microcontrollers.
The maximum supported JTAG speed is 8MHz.
Yes, you can access all individual ICE registers via SAM-ICE.
Yes, the status of all pins can be read. This includes the outputs of SAM-ICE as well as the supply voltage and can be useful to detect hardware problems on the target system.
No. ETM requires another connection to the ARM chip and a CPU with built-in ETM.