A: Yes, this scoop can be used for sunflower seeds.
A: it does work with sunflower seeds but not well. the sliding mechanism isnt always smooth/easy mine eventually broke off. the sunflower seeds sometimes get bottled up and you have to shake it a little. you need two hands to use it also so its not too user friendly. the best seed scoop is droll yankees seed scoop its blue in color. the droll yankees can be used one handed, holds enough to fill two feeders, all seeds flow through including dried mealworms, and it can be set down without spilling any seed.
A: Yes and it is the only seed I use.
A: Yes. I use sunflower feed and peanut mixture. Works great. I have a Gazebo Bird-feeder and needs filled through a hole in the top. Very hard to pour so I bought this because of the neck to align with the hole in the top. It is to big to go in side but I just hold it there and then open it up and the seeds pour easily into the hole. I really like it