Answer 1

use pytube library to download the video, then use ffmpeg on your machine to extract audio from the video stream, then you can use pydub to extract specific audio fragments or you can try the same with ffmpeg itself

Answer 2

Sayantan well, you will most likely need to download the entire file. i doubt youtube easily supports chunked downloads. see this tool too, which yiu can start as a process from any python https://askubuntu.com/questions/178481/how-to-download-an-mp3-track-from-a-youtube-video

then call ffmpeg as a process from python https://stackoverflow.com/questions/20295398/ffmpeg-clip-audio-interval-with-starting-and-end-time