Collar interfacing and button placket

Hi Just checking the collar view A requires interfacing for BOTH collar stand pieces ( pattern pieces indicate so but p3 step 5 doesn't show any interfacing? ) View A Both sides are identical? And button placket needs to be edgestitched on innermost fold - p2 step 2 but later pictures ( and other shirts) have edgestitching on either side of RH placket. Please could you clarify. Thx. I'm doing it for our pattern review at Guthrie Ghani so want to follow instructions exactly. Thank you