Hello,
3/ Single product builder > https://prnt.sc/PubJp_fekyql , so go to Appearance > Widgets > add content into this area https://prnt.sc/IsX3YJ_drXnh
4/ I am not sure that fully understand your request. Please describe the desired result in more detail, one more time. Thanks in advance.
5/ Single Product Builder > https://prnt.sc/sPwFbKhCU9CH https://prnt.sc/feMJXZcRzUwm Is this what you are looking for?
Regards