Desperate for clarification!! ltcg or stcg?

My father got a residential plot alloted under HUDA scheme in 2004. He passed away in 2008 and the property till date hasn't been registered. Currently I'm in the process of getting the title transfered into my mothers name as shes the heir to the property and should be done by September 2018 by when I'll also get the property registered in her name. I am now looking at selling this property. My question is that for the purposes of Capital gains calculations does the holding period start from the date of allotment or from the date of registry of the property? Entire payment for the property still hasn't been made. Some payment was made initially. Possession was offerered around 2011-2012 but was not taken. If holding period starts from date of allotment, being 2004 in my case, then I'll come under LTCG if it starts from the date of registry then I'll come under STCG. Please help!

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