1) The region that was chosen in the settings determines the sound loudness. The maximum level that can be heard through the headphones will be lower if you choose the region of 2022, but it will be substantially louder if you choose India or another country, like Japan. The volume slider has an additional margin of two clicks to add sound, but the volume does not change, I repeat the volume using good headphones is decent, if anyone does not understand, write a comment, I will attach a photo for a better understanding of ti). When listening to music through the VK application, the sound is added for the final two clicks (if anyone does not understand, write a comment, I will attach a photo for a better understanding of ti).
2) Mobile data transfer is not always connected after connecting to wi-fi in the subway; for example, you can phone but the mobile Internet is not connected. The "flight" mode must be activated for 10 seconds before the mobile Internet is accessible. Since the issue does not constantly arise and does not occur on all subway lines (I take the red, orange, and yellow), it has only so far happened while logging out of the wi-fi in the metro; however, when logging off of the wi-fi at home, everything works as it should. Two variations of this issue exist:
1: The phone is unable to connect to an access point after disconnecting from wi-fi in the subway due to poor connection at various stations (although my device has global firmware, it was initially released for the Chinese market and may not function properly with the frequencies of our mobile operators in subway conditions). I repeat, you can make and receive calls simultaneously, but only the mobile Internet (in my case, 2g (GPRS); I haven't tested it on 3g yet) does not work, and even then, not always (at the same station on different days, after disconnecting from wi-fi, it switches to mobile Internet perfectly and everything works great).
2: After receiving permission to connect to wi-fi in the subway, something either occurs at the hardware level (with communication modules) or via a software jamb (for Xiaomi, firmware jambs are typical).