What about (c) (i), why are there three resonance structures? If a hydrogen is taken away from a specific carbon of the initial molecule to have a radical, there is no way you can have three resonance structures.
The barrier to rotation in the allyl radical is low (~15-16 kcal/m) and it can undergo cis-trans isomerization.
As to question (c)(i), you're right, there are only two resonance structures.
What you show above with three resonance structures is the trimethylenemethane diradical, isobutene with 2 allylic hydrogens removed.