Application of Its Lemma and answering the following questions

Examples of applications are provided below:

Calculating dG for the following questions with dS = 0.1 S dt + 0.2 S dz:

a) G(S,T) = S*e^((r * (T-t)) where r = 0.04 , T-t = 0.5

b) G(S,T)= S^2

c)G(S,T) = S - K where K=100

d) G(S,T) = 1 if S >100; and 0 else

Please provide detailed calculation steps