Hello Khan,
a)
permit 192.168.8.0 0.0.7.255
and
permit 192.168.8.0 0.0.7.0
do different things although in some special cases the second could be used with the same results but no guarantees ...
b)
I don't understand what you mean
I try to guess
if these are the the same octect:
0000 1000
0000 1110
0000 0 match and must match
the last bit match and must match
0000 1000 base address
0000 0110 wildcard mask
hope to help
Giuseppe