ikkyo first then flow into yonkyo or you could say it's short grip ikkyo with a hip rotation and weight drop. personally, i have problem with the elbow in the face approach where you are in range of the other fist or a low side kick or tall uke who would just laugh at you while you are on your tippy toes. or the find the pain point approach where you don't have the other person balance and while you try to find the point, they pasted you.
sankyo is spiral in and up. yonkyo is spiral down and out. sort of a opposite of each other.
of course the higher level of yonkyo is yoinkyo.