What is the difference bw NEST and NOW? In which case NOW can be useful?

Copy pasting from FAQ page, https://zerodha.com/faq

  1. We offer different platforms - Desktop, Web, and Mobile. 
    NEST(ZT), Zerodha mobile, and trade.zerodha.com are platforms built by vendors (Thomson Reuters). The user interface, charting, and tools on these are average. 

    Pi (desktop version) and Kite (web/mobile) are our in-house trading platforms; the user interface matches international standards.

    NOW is an alternative provided to a few clients who want to use NSE’s own trading platform. We don’t recommend this and do not support it. 98% of our clients use ZT and/or Pi.

NOW being NSE platform, you can trade only on scrips listed on NSE on it. You also don't get features like cover or bracket orders. 

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