Some problems about Korean pronunciation

1.？ And then what? There is no distinction, the former is S and the latter is Z. The ts you hear is just a colloquial question. These two sounds are uncertain, and the pronunciation is often changed according to the context.

2.？ No inflections, just send n, only? It is possible to turn into a t when listening to the radio.

3.？ Read r in Korean and l in Korean.