Class A - 0.0.0.0 - 127.255.255.255
Class B - 188.8.131.52 - 184.108.40.206
Class C - 192.0.0.0 - 220.127.116.11
These are the correct numbers. The loopback address falls into the class A section, but it is reserved in IP. The range is 127.0.0.0 - 127.255.255.255
Class A - 10.0.0.0 - 10.255.255.255
Class B - 172.16.0.0 - 172.31.255.255
Class C - 192.168.0.0 -192.168.255.255
127.0.0.1 is not a member of class A and any other class. It is your NIC's loopback. So, no matter what happen, even if your not in any other network you can still ping 127.0.0.1.
about the subnets, just refer to the power of 2's.
for your question, its 128 (1,2,4,8,16,32,64,128,256).
126 is the number of usable ip address in that subnet.