1.) Does ends justify the means?
Well firstly the "formal theory name" is Kant's Categorical Imperative, which endorses "ends justify's the means" so if you're still curious you can google this.
Yes it does: As you mentioned the Robbin Hood example, the ADA obtaining evidence illegally, both of these things helped the majority supported by a theory called utilitarianism, the action that does the greatest good for the greatest number of people is always justified. War is often justified by this for example, the irony of peace achieved through violence.
No it doesn't: Ok, but who is to decide what is just? What is Robin Hood was corrupt like other thieves and kept the money for himself? What if the ADA had been bought by some friend of the molestor to lose the case on purpose? What is the government declaring the war was corrupt and was only attacking a country, say only for it's oil reserves? This leads to the "slippery slope" arguement...power can corrupt.
Alright I'll stop, I can go on and on for either side 😆 Basically, it depends on the situation, it can't be applied generally.