GST on Asset

If You are take that ITC then Yes GST applicable for the sale of Car.

Yes GST applicable in this transaction

But I purchased it in vat period not in GST regime

Yes... But, Sale proceeds in GST regime and GST applicable on sale value.

As per Notification 8/2018 CT (r)
Vehicle of Vat Regime Sold in GST Regime : GST is applicable on Profit Margin (Sale-Puchase )

Vehicle Purchased & Sold in GST Regime : If ITC claim , then GST is on transaction Value If ITC is not claim , then GST is on Profit Margin (Sale - Purchase)

GST Rate 12 % & 18% is applicable as per CC engine of vehicle mentioned in Notification. More then 1500 CC , leanth exceeding 4000 MM, GST is 18% Else ,.. 12%

Note: Government also Exempted the Cess applicable on sale of Used vehicle through Notification No. 1/2018 Compensation Cess Rateunder entry no.42A

GST is applicable in this transaction. It constitutes a Supply.

Refer Notification No. 8/2018 - CT ( RATE ).