Вы могли бы предупредить его заране

Вы могли бы предупредить его заранее, что он должен был прийти в 5 часов.

Результаты (английский) 1:

You could warn him in advance that he had come to the 5:00.

Результаты (английский) 2:

You could warn him in advance that he was supposed to come at 5 o'clock.

Результаты (английский) 3:

you could have warned him beforehand that he was supposed to come in 5 hours.