First, your little one is still very little. She has big feelings, which are normal, and needs a lot of boundaries and guidelines from you.
One thing I would work on first is ensuring that your eldest daughter has a place to play alone, without her little sister interfering. Consider putting a swinging gate in her doorway, so she can play in her room with the door open without having her toys taken. If that doesn't work, find another way of keeping your younger one separate. Little toys a problem? Consider setting up a pack-n-play and letting your older one sit in there with the small pieces. I did this quite often as a nanny and it worked pretty well.
Your littlest one needs your calm guidance. "Suzy's playing with that one now. Let's go find something for you." I'd also be clear that "you can have it when she's done" if it's appropriate to that toy.
Since she has a hard time with this "NO", I'd also move her to her room if she has a tantrum. "You can scream in here. Come out when you're done." Tantrums have their place-- in one's room. Don't go in and reason with her, just let her be mad and cool off. Eventually, she will learn that she can have a turn-- it is REALLY hard for them to understand at such a young age. Offer substitutes when you can, see if you can distract/redirect, however, it sounds like you have a very strong-willed little one, so being consistent about NOT giving in is really important. She will learn to just scream until big sister gives her what she wants. You might consider reinforcing this by taking her away from her big sister when she screams so as not to make it your oldest child's problem to solve by acquiescing. "You may not scream as sister. Come on, lets go to (your room, my room, anywhere else)." Provide coaching for 'asking nicely' when you can, and consider giving your eldest a lots of positive feedback when she does what you ask-- not give in. "I know she was screaming and so annoying, and you let her figure it out on her own. That's so helpful. We are all teaching her how to ask for things nicely."