"If I sell a block of land that I purchased more than 12 months...

"If I sell a block of land that I purchased more than 12 months ago, are the interest payments and additional expenses incurred during ownership considered a tax deduction by the ATO?"

Going by the various discussions I have had (and my poor memory) with two different accountants, my understanding is...

only if it is a investment property are expenses deductible against capital gains. The 12 months ownership rule is applied for a 50% CG discount

"does that automatically qualify the block of land as my PPOR or would it be considered an investment property?"

No. it becomes a PPOR when you build a house and live in it

but I got conflicting advice on this from one accountant, but two others(1 my accountant, another a friend) said No