Hello Kurnikr,
The artwork posted on deviantart are just custom artwork based on my character's game and is unlikely be include on the final game. However near the end of the game, Trishka could grow as big as the image posted on deviantart depending on how strong your relationship with her will be, but that growth effect isn't permanent, so it will wear off eventually and she will return to her original size over time. There will be a logical reason for this and an explanation will come later in the story. Most growth scenes will not be as drastic as the one near the end game, but it will be the same effect logic as stated previously.
There will be no tragic ending with a character's death in it. But there is one major game ending if the MC messed up his chance with all the girls and returned to his home alone, that's the worst that could happen. There will be only a few bad endings during the main story with some MC deaths if he acts stupidly or by accident, but these are easily avoidable.