a) For most American English speakers there is no difference between these two sentences. However, "She is at my house" could mean that she is parked in front of my house, or sitting on my front steps.
b) If a lawyer or doctor is practicing law or medicine he is performing his duties in actual cases. If an athelete is practicing his sport, he is rehearsing for an actual competition.
c) When the writer says, "We got to talking about..." it expresses a distinct difference from saying, "We talked about..." In the first example got [to] is the verb of the sentence and it means arrived [at]. The reader gets the sense that the conversation had been moving from one subject to the other, and then to modern wonders. Since the meaning of the sentence was that the conversation had moved, we need to know where it had gone. Therefore, a verb (talk) would not have been appropriate in that part of the sentence. It required a noun or a word functioning as a noun. We got to school...the station...singing about...playing with...etc.
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