candy
Yes, it doesn't have to be something expensive. A coffee mug that has a cap and gown.
No
Both bring something or else it's not fair
When you are invited to a party at someone's home, it is polite to ask whether there is anything that you can bring. If the host suggests that you could bring a dessert or prepare a dish, go ahead.
Unless the invitation or the person or people having the retirement party have requested not to bring gifts to the retirement party then you should bring a gift.
What one should bring to a company Christmas party depends on where the party is being held. If no one specific person is holding it and it is being held at the company office, then the company itself might be providing food and drink, so it wouldn't be necessary to bring anything. If it is being held at someone's house then it might be a good idea to ask the host what one should bring. Party food such as chips/ crisps or chocolate or wine would be good items to bring for example.
yes the should
Because we should!
You should never bring a third party to a person's home or someone who has invited you out to a restaurant until you phone them and explain the situation.
It depends on the usage.
yes
Yes, students should be allowed to bring snacks to school. It helps you think.