1. Our teacher dilated on this sentence structure in class. ('Dilate' is the wrong word to use in this sentence. See http://learnersdictionary.com/definition/dilate) Sentences 2, 3, and 4 our correct. These examples do not use the words 'in' and 'on' as prepositions of place, rather these are preposition-verb collocations. How we know whether to use 'in' or 'on' depends upon the verb they follow. Unfortunately, for language learners, this usually means memorizing lists. Here's a good one for you to use: http://eslgold.com/grammar/verb_preposition_collocations/

Hi Salvater; They are not interchangeable. "On" refers to the entire sentence. "In" refers to a single word, clause or phrase within the sentence. "With" could be used interchangeably. I hope this helps. Thanks, Stephen