Is there an option in CAESAR to get the two separate code stresses as per EN13480
sigma3 - calculated as per equation 12.3.4-1 and
sigma4 - calculated as per equation 12.3.4-2 ?

Yes.

Equation 12.3.4-1 is termed the "conservative" approach while Equation 12.3.4-2 is termed the "liberal" approach. In CAESAR II, the (Pd/4e+.75iMa/Z) part of 12.3.4-2 is subtracted from both sides of the equation. This gives the same expansion stress range equation as you find in all other power and process Codes.