How does putting a の at the end of a sentence change the meaning?
For example, here are some sentences:
明日何時に来るの What time will you come tomorrow
昨日何を食べたの What did you eat yesterday
Generally speaking a sentence ending in の will be less formal equivalent of the "の／んです" construction. Hence:
2) I have also assumed your focus is on questions: Sentences that are not questions using "の／んです" (and its variants) are used for explanation, rapport, reproach and "backgrounding". This is covered in the same reference given below. [I would classify "soft sounding affirmation" discussed below as an example of rapport.]
Ref: A students' guide to Japanese Grammar, Naomi Hanaoka McGloin, p89/90
As you seem to have already answered yourself in your own translations, "の" with accent/intonation in the end turns a sentence into a question.
Note however that if you don't put such an emphasis in the end, "の" just act as a slight softner of the sentence and doesn't turn the sentence into a question. This form sounds like a child speak, so I don't recommend you use it yourself.