ahsmall

I am not sure if you need to provide them with the proof because HK Immigration should have your record about entering and leaving HK already.

About the year of birth - 1964, you can check the following website
http://www.smartid.gov.hk/tc/replace/index.html#02

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1964 或 1965  -> 2004年1月12日 至 2004年3月13日
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If you need to provide the proof, then the proof for the above period should be enough.

About invalid HKID, just use the old one since your friend was not in HK at that time. If he/she also has HKSAR passport, also brings it back to HK