only在句首的主语倒装在only和主语之间,可能会加一些情态动词,哪么怎么会有加did或其他助动词的现象呢?

全倒装句型（1）
here，there，out，in，，up，down，now，then等副词放在句首，句子需全倒装；
There goes the bell!=The bell is ringing!
There lived an old man.
Here comes the bus.=The bus is coming.
Out rushde the dog.
注意：1.在这种情况下倒装仅限于不及物动词或be动词，想go,come,rush等；
2.主语如果是代词时不需要倒装。
Anyway he went.他走远了。
全倒装句型（2）
方位状语在句首，句子全倒装
In front the house stopped a police car.
全倒装句型（3）
adj./v.-ing/v.-ed +(地点状语)+be...
Present at the meeting were the manager,all the designers and the writer.
Sitting at the back of the classroom were several old teacher ,listening attentively to the new teacher.
Gone are the days when farmers live in the poor houses.
半倒装句型（1）
否定意义的副词或短语在句首，句子半倒装，例如：little,never,hardly,rarely,seldom,not at all,by no means等。
Never shall I forget you.
At no time was the man aware of what was happening.
little did I understand what he said to me at that time.
半倒装句型（2）
Not only...,but also...
Not only was everthing he had taken away from him,but also his German citizenship was taken away.
They suggested not only should we attend the party but also give a performance.=They suggested us giving a performance as well as attending the party.
Not only should we students study hard, we also should know how to enjoy ourselves in our spare time.
半倒装句型（3）
neither，nor放在句首
If you don't go to see the film ,neither will I.
Why didn't you buy it?
Neither was the price satisfatory,nor did the colour agree with me.
I don't like him,nor do care I about him.
半倒装句型（5）
Only + 状语 放在句首，主句半倒装
Only when the war was over did he return to work.
半倒装句型（5）
Many a time;ofter ;once in a while等频度副词放在句首
Many a time has helped me with my English.
半倒装句型（6）
so + 助动词 + 主语“也..."
She is intereted in the story, so am I.
He enjoys playing the guitar,so do I.
I saw the flim last night ,so did he.
我昨晚看了电影，他也看了。

我没听懂你是什么什么意思，但only 后要加倒装。
Eg.
Only then will I have a chance of achieving my dreams.

加did因为是在过去时里.
若句中有情态动词就把情态动词放到主语前,若句子里没有情态动词,就用助动词do的适当形式.