1) Screen Shots of the STB software interface and the STB hardware are available in other threads of this 'Reliance Jio Fiber' forum. Check them out.
2) Hotstar, SunNXT, SonyLIV, Zee5, YouTube and Voot are the only apps available in the Jio STB as of now. Netflix and Prime Video are not available. At least not yet. Neither is MXPlayer TV.
3) Also, even the YouTube app in this STB can play only up to 1080p video. The STB does not support 4K / 4K HDR yet.
4) A few additional LIVE TV Channels are available in an app called JIO TV+.