Rules, you don't need rules. These are your beloved DC, not employees. If you are doing it right, there will be respect on both sides and you muddle along working things out as you go.
Food; They will eat enough, don't make it a battlefield. Offer healthy food, if they don't eat it, give toast.
Beds; if ours were scared in the night they knew they were welcome to get in with us however old they were. They hardly ever did though.
School; Not really important, If they wanted a duvet day fine! I've even done their homework so they could play out. Mental health is more important. Funnily enough, all 3 of them are now educated to masters level.
Family; The more people that love your child the better, so work on family links, even if you don't get on with your parents or in laws, your DC might.
Teenagers; Pick your battles, compromise to find a safer way, Don't be afraid to have a row occasionally. Forgiveness is good.
Alcohol, well ours were having a tot of wine with meals since about age 10. They hardly ever drink now.
Drugs; Talk, talk , talk to them about the risks. AFAIK all of my DC are anti drug, they are in professions where drug misuse would not be tolerated.
Gender; Whatever.