Here are the correct forms of the words in brackets:

1. His company designs and makes **decorations** glassware and soft furnishings, as well as offering a full design and decorating service. (decorate)
2. Setting off firecrackers can add to the **festive** atmosphere and offer a way for people’s pleasure and excitement. (festival)
3. In my village, it is a **custom** for a girl to take her mother’s name. (custom)
4. The purpose of the UN is the **maintenance** of international peace and security. (maintain)
5. During Tet, the Vietnamese prepare to worship their ancestors during **traditions**. (tradition)
6. They perform martial arts and acrobatics in the festival on **occasion**. (occasion)
7. The exhibition consists of more than 400 religious artifacts and **ceremonial** objects. (ceremony)
8. These activities often lead to lots of laughter and fun **conversely**. (converse)
9. A lot of **participants** perform in the show, showcasing their incredible talent and entertaining the audience with their unique skills. (celebrate)
10. In the game, **contestants** were grouped according to age and ability. (contest)