1 I wouldn't accept if you asked me to marry you

=> Were you to ask me to marry you, I wouldn't accept

Đảo ngữ câu đk loại 2 động từ thường: Were + S + (not) + to V … + S + would/might/could + V

2 I didn't realize you were tired when I asked you to go for a walk

=> Had I realized you were tired, I wouldn't have asked you to go for a walk.

Đảo ngữ câu đk loại 3 động từ thường: Had + S + (not) + P2 +... + S + would/might/could + have + P2

`1`. Were you to ask me to marry you, I wouldn't accept.

`->` Đảo ngữ điều kiện loại `2`: Were + S + O/to-V, S + would (not) + V-inf 

`2`. Had I realized you were tired, I wouldn't have asked you to go for a walk.

`->` Đảo ngữ điều kiện loại `3`: Had + S + V-pII, S + would (not) have + V-pII