This is to send a Gift Aid claim form to the Inland Revenue in the UK. The form must be on ODF format
All the versions are available from TDF download archive. But it’s unclear why you need 3.5 to send an ODF? LibreOffice’s native format is ODF, and naturally, latest versions also produce ODFs just fine.
Heh, found a mention of the 3.5 
- well, what can I say. They have apparently forgot to mention “… or later”
I think you need LibO 3.5 or later because 3.5 supports ODF 1.2. Really the requirement is to support at least this level of ODF. I presume any software that supports ODF 1.2 would work.