Till is less formal way of saying until. Till and until are interchangeable but till is more informal than until, and in writing, when we start a sentence with these type of preposition the preference is always until. )

hmmm

Till is just a contraction of until, so I think they are interchangeable in that sense. It seems to me it's a personal choice of which one to use, and it seems to depend on how it fits into the sentence....But there are some expresions in wich you MUST use 'till'. For example: I usually work from morning TILL night...i hope it will help...:)

There is no difference. I guess.^^

As conjunctions and prepositions, the words are synonyms. Till has some other meanings as noun and verb.