Well, it's not easy to say off the top of my head. Different manga series might number their chapters differently for the Shibuya Arc. You could try searching on manga-specific websites or asking in manga communities for the accurate chapter.
Well, it's a bit hard to keep track precisely. Different sources might have different updates. But you can usually find the current arc mentioned on manga-related websites or social media groups dedicated to JJK.
The answer is: "OST song" refers to the song in the OST. OST referred to the original music in movies, TV series, and other film and television works, and the song part was the OST song. According to the search results, some OSTs of movies and television works included some songs, such as the theme song of the TV series OST of " A Thought of Passing Mountains," many of Zhou Shen's OST songs, and Yu Kewei's Top Ten Classic OSTs. Therefore, an OST song referred to the song part of the original music in a film or television work.
The OST lineup for the second season of Celebrating Years had already been announced. Among them, Li Jian sang the theme song " In My Lifetime," Zhou Shen sang the ending song " Excuse me," Liang Long, Liu Duanduan, Zhang Haowei, and Guo Zifan performed the promotional song " Aiya." These songs would bring more musical elements to the second season of " Celebrating Years," adding more emotions and atmosphere to the plot.
I'm not entirely sure as it could be a specific visual novel related to Shibuya. It might involve stories set in Shibuya, with characters experiencing various adventures, romances or mysteries in that location.