Can an under 18 service alcohol in a restaurant?

Not alcohol, no. It depends where you are. In Scotland: The law on what age a person can drink alcohol is complicated. Before the age of 18, you are not allowed to buy alcohol in pubs or shops, or drink alcohol in pubs. It is also unlawful for anyone else to buy alcohol for a person aged under 18 to consume in a pub. If you are aged 16 or 17 you are entitled to drink wine, cider or beer to accompany a meal in a hotel or restaurant. Any child over the age of five can drink alcohol at home or on other private premises. It is an offence to give alcohol to a child under 5, even in her/his own home. Source: http://tinyurl.com/8n7j43