Why collector current is inwards to transistor in an NPN?
You can get a multimeter and satisfy yourself of the existence of two diodes inside an NPN transistor but that doesn't mean it makes sense to imagine that a BJT relies on that fact for its operation.

The collector-base region IS reverse biased and the diode shown in the question IS therefore shown correctly. Also, just because the collector-base is reverse biased doesn't mean that no current can flow. Study the BJT and you will (eventually) understand that electrons are carried across the base into the collector region because the reverse bias IS present: -



A BJT isn't just two diodes built inside one package.