HLE Application - Need to submit at one go?

I understand that HLE is required to be applied before can get a BTO?

I am shock as I thought i could submit HLE application after I apply for BTO and while waiting for the ballot, I then apply my HLE..

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I also want to check if HLE needs to be submitted all in one go? I heard previously that one applicant can first fill in the details and save the draft and there is a link to be send to the other applicant to fill in the rest of the information. How does that work if anyone here knows?

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Because i am PR and I cant submit as first applicant. Does that mean i need to log in to my finacee account to submit the rest of the documents or what? there is no guide i can find in the internet now :( someone please help.