Answer 1

Something like:
context.delete(obj)
or
context.deleteObject(obj)
Where obj would be an Item in an array of the Items (objs) within the context returned from an executed fetch request.
You will usually loop over them to delete them all.

for obj in objs {
context.delete(obj)
}

Don't forget to save afterwards.
context.save()

Sorry, it's been a bit since I've used Swift with iOS, but hopefully you can figure it out from this.