@hello299 . You may use Sling Post Servlet to update properties by POST call to jcr:content path. You may import the below curl command(update auth headers if needed) into Postman and execute it for batch if required.
curl --location --request POST 'http://localhost:4502/content/xyz/language/en-us/abc/pqr/jcr:content' \
--header 'Authorization: Basic YWRtaW46YWRtaW4=' \
--header 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'cq:lastModified=2018-05-11T11:45:03.673+05:30' \
--data-urlencode 'cq:lastModified@TypeHint=Date'
But there is an observation when you update cq:lastModified property via Sling Post, it updates the property back again to current modified timestamp. AFAIK, you have to do some custom script development for your correction and use that endpoint.
ResourceResolver resourceResolver = request.getResourceResolver();
Resource resource = resourceResolver .getResource("<pagepath>/jcr:content");
ModifiableValueMap modifiableValueMap = resource.adaptTo(ModifiableValueMap.class);
modifiableValueMap.put("cq:lastModified", <date value>);
resourceResolver.commit();