What is correct .... “is complete/completed”.....?

What is correct .... “is complete/completed”.....??? For example in the following sentence: The actual change will not take effect until the status stage of this command is successfully complete/completed. >> I think “complete is only correct. Complete is an adj. and successfully is the adv. that tells... show more What is correct .... “is complete/completed”.....???
For example in the following sentence:
The actual change will not take effect until the status stage of this command is successfully complete/completed.
>> I think “complete is only correct. Complete is an adj. and successfully is the adv. that tells more about adj. that follows.
One can also use done/accomplished in place of complete. But I guess using completed would be wrong.

On http://www.usingenglish.com/forum/ask-teacher/9925-soon-transaction-complete-completed.html it is
mentioned that both the statements given below are correct.
1a. Your credit is being processed. As soon as this transaction is
complete, you will receive an email confirmation.

1b. Your credit is being processed. As soon as this transaction is
completed, you will receive an email confirmation.

It is also mentioned on the site that difference in their meaning is: [but it still not clear to me  ]
1a means => All in order
1b means => Finished

Can someone explain if 1b is grammatically 100% correct?
Can someone help me understand what is the difference in their meaning, if any?
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