Ans 3:
Class : Class 8
Tomorrow must be changed to 'the next day' when we change a sentence from direct to indirect speech
Ans 5:
Class : Class 7
It should be 'none of these'. The passive voice will be 'The Met. office said that it would rain heavily the next day.'
Ans 6:
Class : Class 7
I think I would like to go with option c which is-The Met. office says that it would be raining tomorrow.