There is no difference.

No, all three are pronounced the same, but, as I'm sure you know, all three words have a different meaning.

The main difference you should focus on is that "to" always has a weak accent, whereas "two" and "too" have strong accents. So yes, we can hear the difference but it's a matter of stress; not the actual pronunciation of to/two/too, which is the same.

They are not pronounced quite the same. The preposition "to" is pronounced the same as the words "too" and "two" only when it is followed by a word beginning with a vowel. It is pronounced as [tu:]. Before a word beginning with a consonant it is pronounced [tә], whereas the "o" is neutral or "schwa" sound.

トゥー、トゥー、トゥー