Is it ok to call again SDL_Init after SDL_Quit?
Yes, it should be okay to call SDL_init() after SDL_Quit() has been called, i.e to startup SDL again. Normally you wouldn’t need to do that though, since SDL is usually initialized at the startup of the program/game and closed at program/game shutdown, and then, during runtime, SDL_Init() and SDL_Quit() aren’t usually touched.