Hi Shripal,
LINS's depreciartion is based on Net book value which is equivalent to WDV so dont worry about the text in dep key whether it is staright line or WDV.
Regarding dep to day: If your company already operating dep to the day functionality then you have to create a clone of LINS(Copy LINS) and create a customised dep key. In the customised dep key activate the dep to day functionality. Then use the said dep key in all assets.
Test the scenario in quality client and you will find the result is matching as per companies act 2013.
Hope it solves.
Regards,
G.Sethuaraman