Often times you'll find that there doesn't exist information for exactly what it is you want to do on the internet.
But you can find tutorials for things that are close.
I imagine if you look for how to make platformers in Unity you'll get some useful results. Probably for metroidvania style games as well.
As for making a weapon with that particular behavior, that's going to be trickier. You'll need to decide what exactly happens when someone swings a whip like that, and determine how to represent it.
Programming in general is like this, but in video game programming especially you'll frequently come across vague, strange problems that are difficult to resolve. What you need to do is break things down define what it is you want to accomplish.
This is part of why I suggested looking at some tutorials. That will give you some context. While this might not even help you determine how to implement your desired feature? You'll have a better idea of how to ask for help.
If on the other hand you already did do all that and are just really uncertain of how to represent a whip that bounces all over the place? Frankly I don't blame you. That's a difficult problem.
There's a few ways I think you could go with this, so I'd say the first thing to do is settle on and visualize the specific way in which you want the whip to work.
Probably your answer is to use several hit boxes. Make an approximation of a flailing morning star.
Sorry if my answer is a bit long and rambling.