I'm still reviewing this, and my terminology is still a bit off, but I would approach this as follows....(Keep in mind I could be mistaken, and I'm sure one of the wonderful CCIE's on here will let us know)
Switch 3 is the Root, therefore all interfaces on that switch are FWD
Switch 1 and Switch 4 both have RP's tied directly to the Root,
This leaves us with the following interfaces/switches
The port that would block is SW2, Gi0/2 if you assume all req's are =, it will come down to port #, and the lower port will fwd.
RSTP Process for port discarding is
1 - Lowest Cost Path to root
2 - Lowest switch ID
3 - Multi-connections to root use lowest priority (if same see 4)
4 - If 1-3 don't solve, then the port used will be the lower port # (So the higher port will be discarding).
SW2 - Gi0/2 is also my answer.
If you take the cost of the interfaces into account, will you still arrive at the answers you replied with? If I'm correct STP cost of Fa = 19 and Gi = 4.... Please post your views taking this into account.... Also, the cost is based upon link or interface????
Switch 1's cost to the root is 19 via its direct connection, so this is the cost it reports. Switch 2 on the other hand has to report a cost of 23, its Gi interface connecting to switch 4 has a cost of 4, but switch 4's connection to the root has a cost of 19, so the total cost is 23. Even though switch 4 has a Gi interface to the root, the cost of that link is 19, because of the Fa interface on the root. Least cost path to the root wins.
I think it's FA0/2
on switch 1 to block the loop.
cost for switch 2 is lower through the gi interface to reach root. switch 3 is root based on lower mac address.
I may be incorrect though
Switch 2 is right due to lower port number. lower is better in stp