Can you create a story based on the first and last sentences from public domain novels?
Well, it's possible. Suppose the first sentence is 'Once upon a time, a young adventurer set out on a journey' and the last sentence is 'The adventurer returned home, a changed person'. I would start by elaborating on the reasons for the adventurer's journey, the challenges faced during the journey such as meeting dangerous creatures, getting lost in unknown terrains. Then show how these experiences transformed the adventurer so that when he returned home, he was a different person.
Sure. But it depends on what those first and last sentences are. Without specific sentences, it's hard to start. However, generally, if the first sentence sets a scene like 'It was a dark and stormy night' and the last sentence is something like 'And they lived happily ever after', I could create a story about a character facing difficulties during the storm but ultimately finding peace and love.