Since the sale deed has been fraudulently executed impersonating your mother by a registered deed, you may have to file a suit to cancel the registered sale deed.
Who is in possession and enjoyment of the property, if your mother is not in possession and the possession s held by the so called buyer, then she may have to even seek possession in the same suit.
The civil suit has nothing to do with the criminal complaint, hence she can file the suit as suggested immediately before it is barred by limitation.
Declaration suit may not be necessary but a suit for cancellation of the registered deed may be filed in order to remove the encumbrance against the property.
What will be the3 purpose of filing perpetual injunction suit.
Perpetual means permanent. Perpetual injunction is one that is granted by the judgment that ultimately disposes of the injunction suit.
The permanent injunction suit if decided in your favor may restrain the party to use the sale deed in his favor but that will not help you to clear the encumbrance created against your property which will remain as an adverse impact.
The injunction suit will not in any manner come to your rescue either to change the revenue records or the removal of encumbrance created in the property.
Also this injunction suit will not provide you the clear and marketable title to your mother which was damaged by the registered sale deed now standing in the name of the buyer.
Even though you say that somebody impersonated your mother to execute a registered sale deed in favor of the buyer, the criminal case against the fraudster will not help you to regain the title to your mother's name until the sale deed is cancelled by an order of the court and also the encumbrance is removed by the same order of the court.