Answer from cs61c-ee (Michael Shen 15963205) for Question 1
EPC is a 32-bit register used to hold the address of the offending instruction which could include an overflow or an undefined instruction.
The cause register is used to store the cause of the exception.  It encodes bits to mean certain things so that for example the lower order bit signifies eihter an undefined instruciton or an overflow.
The two instructions that cause exceptions are undefined instructions which are detected when the next state is not defined by the op value of the instruction.  Arithmetic overflow also causes exceptions.