I have 2 orgs. I want to retrive particular account records from another org to my current org, using rest api 
I'm using custom domain name on second org.
Its look like https://nara-narayana-dev-ed.my.salesforce.com/

On my current org code that respons for creating request looks like 

Httprequest req=new httprequest();
        String domainName='nara-narayana-dev-ed-c.eu6.visual.force.com';

        String endPointURL='https://'+domainName+'/services/apexrest/Account/0015800000FvETO';
        req.setendpoint(endPointURL);
        req.setHeader('Content-Type', 'application/xml; charset=utf-8');
        req.setmethod('GET');
        req.setHeader('Authorization','Bearer '+ UserInfo.getSessionId());
        Http http = new Http();
        HTTPResponse res = http.send(req);
         String response=res.getbody();
        System.debug('****************res.getStatusCode();'+res.getStatusCode());
        System.debug('****************res.getbody();'+res.getBody());

Rest resourse on second org looks like:(for simplicity, its now returns string 'hello')

@RestResource(urlMapping='/Account/*')
global with sharing class AccountManager {

    @HttpGet
    global static String getAccountById() {
        RestRequest req = RestContext.request;
        /*String accId = req.requestURI.substring(
                req.requestURI.lastIndexOf('/') + 1);
        Account result = [
                SELECT Name
                FROM Account
                WHERE Id = :accId
        ];*/
        return 'hello';
    }

    @HttpPost
    global static String createAccount(String name) {
        Account acc = new Account(
                Name = name);
        insert acc;
        return acc.Id;
    }
}

As a result i'm getting [{"errorCode":"NOT_FOUND","message":"Could not find a match for URL /Account/0015800000FvETO"}]
in debug log and status code is 404. So I assume its something wrong with endpoint url. How to make it correct?

Also I have added this url https://nara-narayana-dev-ed.my.salesforce.com  to Remote site settings