Here are the rewritten sentences as requested:

42. The last time Vietnam hosted the Sea Games was in 2021.
→ Vietnam hasn't hosted the Sea Games since 2021.

43. "I won't eat the vegetables," said my daughter.
→ My daughter said that she wouldn't eat the vegetables.

44. There was a power cut last night because of the violent storm.
→ Because the storm was violent, there was a power cut last night.

45. People believe that General Võ Nguyên Giáp is a political and military genius of the Hồ Chí Minh era.
→ General Võ Nguyên Giáp is believed to be a political and military genius of the Hồ Chí Minh era.

46. It is advisable to breathe deeply when you feel stressed. (SHOULD)
→ You should breathe deeply when you feel stressed.

47. I'm thinking with pleasure about my summer holiday. (FORWARD)
→ I'm looking forward to my summer holiday.

48. Smoking is harmful to your health. It is also costly. (But)
→ Not only is smoking harmful to your health, but it is also costly.

49. It is hard to say why their relationship is getting worse and worse. (MAKES)
→ It is hard to say what makes their relationship get worse and worse.

50. We went to bed early because we were very tired. (SO)
→ We were so tired that we went to bed early.