Thus, the instant appeal before us.   The Issues   OSCI raises the following issues for our consideration:   a. Whether or not it is contrary to the principles of res judicata for the Court of Appeals to have ordered the reinstatement of Labor Arbiter Mayor’s Decision dated 28 January 1999 which was already vacated and set aside by the NLRC’s Resolution dated 30 July 1999 which in turn has become final and executory without respondent questioning the same.   b. Whether or not it is contrary to the legal principles of the “law of the case” for the Court of Appeals to have disregarded the findings of the NLRC in the latter’s Resolution dated 30 July 1999 which by law is already final and executory.   c. Whether or not it was grave and reversible error on the part of the Court of Appeals to have sanctioned Labor Arbiter Lustria’s departure from accepted procedure in admitting into evidence the gravely belated submissions of respondent without any justifiable reason being advanced for said belated filing.   d. Whether or not the Court of Appeals erred in recognizing in favor of respondent a declaration of disability grade 1 by an alleged doctor who is not the company-designated physician and whose competence was not established.   e. Whether or not the lack of a proper verification of the Position Paper and/or Manifestation/Compliance filed by respondent before Labor Arbiter Lustria rendered said pleadings without legal effect as an unsigned pleading provided by Sec. 4 in relation to Sec. 3, both of Rule 7.   f. Whether or not respondent’s complaint for disability filed with the Labor Arbiter should have been dismissed for failure to be supported by a