Ans) You can get them by shopping in-store. You have to use the digital coupons for only the items which you have selected upon purchasing the digital coupons.
Ans) No. It allows you to combine a manufacturer's coupon with a Publix coupon or with a competitor's coupon, but not both.
Ans) Yes, Publix accepts the coupons that were valid on the date the rain check was issued.
Ans) It depends upon the manufacturer, if he allows then you can use a coupon more than once. However, most coupons can be used only once.