Capital gain tax on sale of the deed of release property

On inheritance no tax but on sale of gifted property also there is capital gain.

Yes, capital gain doesn't arise when you acquire property by inheritance but capital gain arises when you sold your inherited property.
capital gain arises in the year of transfer.
long capital gains = sale consideration you
received
(-)
indexed cost of acquisition ( i.e
purchase value incurred by your
mother)
(-) indexed cost of improvement
incurred by your mother and
by you till transfer

taxable rate is 20%on such long term capital gains u/s 112