1> How can i view different routes between two places?
In voice navigation mode, there are three icons on the bottom right. Click the middle icon. That will show the different routes on the maps. Tabs will also appear on the top of the screen. Each tab corresponds to a different route. Eg. Three tab for three routes. Select your desired route by clicking the tab or the route itself, then press the arrow on the bottom left & you've been re-routed.
2> I didn't understand the traffic analogies and its representations with different colours, please tell more about this.
See here.
Traffic color descriptions - Maps Help
Green means that traffic conditions are good, yellow means fair, and red or red/black means poor traffic conditions
3> How can i find nearest ATM/Hotel/Supermarket when i'm on the way to somewhere?
When in navigation mode, go to Options -> Layers. You will have Petrol Stations, ATMs etc. Don't know about supermarkets though.
4> Sometimes, the navigation shows wrong points as a destination, how to report it, or help improving.
That has to done in
google maps (not navigation mode) on your phone. Or on your computer. There will be an option to 'Report a problem'.