amendment is not required
you have sought cancellation of the sale deed in your prayer/relief
why that cancellation is sought for, the reasons are mentioned in the plaint so far the factual aspects are concerned
s.22 being a legal point is not required to be specifically pleaded
it is a law point
it can be raised at any stage and even in absence of pleadings in that regard
only facts have to be pleaded. not the law. law is as it is. if the law says that before effecting any sale the right of pre-emption or right of first refusal is required to be exercised, then any sale effected without such mandatory compliance, can be attacked basis such legal plea, even if that plea is not specifically pleaded in the pleadings
so in my view no amendment is needed
however if the issues are not yet framed and the trial has no commenced, then you can apply for amendment
if the trial has commenced and issues framed, then it will be very difficult to amend the plaint