Cats can be fed twice per day and it is best to use quality commercial cat food. All quality commercial cat food packaging always contain recommended daily portions per weight of cat.
You do not need to feed your cat on any schedule and you can leave dry food available for your cats to eat at any time (just make sure that it is not older than one day)
Cats are not dogs and generally stop eating when they have had enough. Cats also usually eat whenever they want to, but feeding your cat on a schedule helps you to understand if your cat is eating too much If your cat is eating too little you need to visit your vet for a health checkup.
Adult cats require as much as 600 calories per day, or more.
Milk : There is no need to give your cat milk (except as a treat) if you are feeding your cat a balanced commerical diet. Quality commercial cat food should already be formulated to contain calcium and other minerals to ensure the health of your cat.
If you are not going to use commercial cat food, cats may become fussy eaters. Either way always ensure to provide a balanced diet with enough (not too much) protein, carbs, minerals and vitamins. Cats should not be fed raw meat or raw fish. diets containing too much red meat could cause calcium and vitamin deficiencies. Diets containing too much fish or too much liver may cause bowel problems.
Cats require essential amino acids, like taurine so cats have higher protein requirements than other animals.
Cats should not be fed commercial dog food, the protein ratios are wrong, the essential amino acid supplements are not added to the formulated commercial dog food. That said, if it is for a single day only, maybe as an emergency, the cat will be fine as the cat will use stored reserves of specifically taurine.