subdomain - 404 error page redirection -

i've setup custom 404 error page using following code.

 errordocument 400 /errors.php 

but when check headers sent see first 301 moved permanently sent followed 404 error header. seo create problem bots.

my second question reg. transfer of non-existent sub-domains 404 error pages.i'm using cpanel , want subdomains created in cpanel work , i've created wildcard redirect non existent subdomain gives me ok status.how redirect 404 page.

thanks.

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