Recruitment rule based on seniority. Can it be dismissed any way?

You have not clarified that how and when were the rules you are talking about in your query made? Whether those rules of recruitment for the posts of primary teachers duly published in the gazzete of the Govt. of Uttarakhand for the said recuitment?

In case the rules have been made and published in the gazzete, we would need the details and acsertain whether the same can be challenged in the competent court of law as the rule is biased towards seniority with respect to the completion of B.Ed and is unfair as the primary ground for hiring in skill based roles must be the competence and capability of the candidate that can be judged by a competitive exam among all the eligible candidates

On the other hand, if the rule is not published and is being followed arbitrarily, the same may be challenged by a Writ in the Ho'ble High Court.