1. The charts that NSE shows may have a lag to it. Kite/PI are trading platforms, data on it as live as it gets.
2. All trading platforms in India offer level 2 data, check this link.
3. Level 3 gives market depth upto 20 best bid/asks whereas level 2 upto 5 bids/asks. The cost of such data is quite high, you will have to subscribe for this from a data vendor. Tick by tick data gives you every tick that happens on the exchange, whereas level 2/level 3 between 4 to 10 ticks a second maximum. But all these costs quite a bit more.
4. Like mentioned above, tick by tick data gives you every single tick that happens on the exchange. Level 1 data just the best bid/ask and LTP.
5. Speed technically is the same, it is just the amount of data that you get. Check this.
6. On Kite/Pi or any platform, you see a market depth which shows you best 5 bids/offers. If you had level 3 data, you could see 20 bids/offers.
7. Check this.
Phew!! that felt like I was writing an exam.. ;)