irfanGaming720/QyuPipe ? reverse-engineered prompt

Build me a lightweight YouTube client for BlackBerry 10 and other older Android devices, with a square 720 by 720 layout that fits a BlackBerry Q10 or Classic really well.

I want it to play videos in a simple, reliable way, with 360p playback by default, subtitle support for VTT, SRT, and YouTube timed text, and a subtitle chooser that lets me switch tracks easily. Put captions in the empty space below the video instead of covering it. Also add background audio with screen off, a dark fullscreen mode, search suggestions as I type, and simple channel pages, watch history, liked videos, and subscriptions saved locally.

Please make it work without Google sign in, use local storage for user data, and include backup and restore for that data. Keep it fast and memory friendly for old hardware, and if you need to check anything, look up current docs online first.