1) Nate, Elliot, and Nikhil have accessory pieces and nude options that unlock when you get the good endings for all four standard routes, but no bonus scenes, as they do not have routes
2) Nikhil is shirtless in a scene and can be naked in his profile if you unlock the option (as per 1 above)
3) Nikhil is straight. Robert is also straight. They will not be routes.
4) I'm glad you enjoyed it!