IV:

2: We are not going to get that contract unless we improve our offer
3: Please don't phone me unless it is an emergency
4: We're going to have a bad year unless demand increases soon
5: This project will not be viable unless you can cut your overheads
6: I won't accept an overseas posting unless I can have my job back when I return

I:

1: hadn't died - would be
2: didn't work - wouldn't have been
3: hadn't wasted - could be
4: were - wouldn't have upset
5: wanted - would move
6: had worked - wouldn't be
7: wouldn't be doing - had known
8: hadn't been delayed - would be
9: hadn't forgotten - would be boarding
10: had followed - might not be

II:

1: you had done
2: wouldn't stand - we hadn't brought

IV.
2. We are not going to get that contract unless we improve our offer.
3. Please don't phone me unless it is an emergency.
4. We are going to have a bad year unless demand increases soon.
5. This project will not be viable unless you cut your overheads.
6. I won't accept an overseas posting unless I can't have my job back when I return.