Yes, it is correct that we cannot use a contracted negative form when we use inverted word order to express unreal or impossible condition in the past. Instead, we are obliged to use the full form of ...

This is a grammar focused lesson using the Third Conditional for ADULT ESL students. It is designed for students who are intermediate level and above. The lesson is based on a text that demonstrates ...

This is a grammar focused lesson using the Second Conditional for ADULT ESL students. It is designed for students who are pre intermediate level and above. It is based on the topic of the Environment ...