how can a disposed case be reopened ?

Yes -a disposed case can be reopened but only by the narrow remedies the law provides: in civil suits by (a) a review petition under Section 114 read with Order XLVII, Rule 1 CPC (limited to mistake or error apparent on the face of the record, discovery of new evidence or other sufficient reason) -see Parsion Devi v. Sumitri Devi, (1997) 8 SCC 715 [https://indiankanoon.org/doc/1922473/] and S. Murali Sundaram v. Jothibai Kannan (2023) (Supreme Court on limits of review) [https://www.courtkutchehry.com/judgements/1155639/s-murali-sundaram-vs-jothibai-kannan-ors/]; (b) setting aside an ex parte decree under Order IX Rule 13 CPC where summons were not duly served or there was sufficient cause for absence [text of Order IX Rule 13; see https://advocatefinder.in/order-9-rule-13-setting-aside-decree-ex-parte-against-defendant/]; (c) restoration of suits dismissed for default under the appropriate Order/Rule (Order IX/Section 151 CPC) or by ordinary appellate/revision remedies. For final Supreme Court judgments, a curative petition (very rare; to prevent gross miscarriage of justice) may be permitted after review -Rupa Ashok Hurra v. Ashok Hurra (2002) (curative jurisdiction). [https://indiankanoon.org/doc/88551377/]. In criminal cases the case can be reopened by appeal, revision, review and, in the rarest of cases, curative remedies under the present criminal statutes; the current penal, procedure and evidence statutes are the Bharatiya Nyaya Sanhita, 2023 (BNS), the Bharatiya Nagarik Suraksha Sanhita, 2023 (BNSS) and the Bharatiya Sakshya Adhiniyam, 2023 (BSA) (bare Acts). [BNS: https://www.mha.gov.in/sites/default/files/250883_english_01042024.pdf] [BNSS: https://www.mha.gov.in/sites/default/files/250884_2_english_01042024.pdf] [BSA: https://www.mha.gov.in/sites/default/files/250882_english_01042024.pdf]