Postgres 10

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select version();

version

PostgreSQL 10.23 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-15), 64-bit

SELECT 1

create table test(id int, data text);

insert into test values(1, '[
 {"code":"ABC","Value":"A1"},
 {"code":"Name","Value":"Ramesh"},
 {"code":"Age","paramValue":"24"}
]');

CREATE TABLE

INSERT 0 1

with cte as (select id, '{'||b-1||',paramValue}' "path_" from test, jsonb_array_elements(data::jsonb) with ordinality t(a,b)
where a->>'code'='Age')

update test t1 set data=jsonb_set(t1.data::jsonb,path_::text[],'"30"'::jsonb) from cte where t1.id=cte.id

UPDATE 1

select *  from test

id
data

1
[{"code": "ABC", "Value": "A1"}, {"code": "Name", "Value": "Ramesh"}, {"code": "Age", "paramValue": "30"}]

SELECT 1