regex - Apache2 - mod_rewrite and .htacess - Not working 404 rule when i add other rules -

here current .htaccess file:

rewriteengine on  rewritecond %{the_request} ^[a-z]+\s([^\s]+)\.php\s  rewriterule .* %1.html [r=301,l] rewriterule ^(.*)\.html$ $1.php   errordocument 404 /page-404.html  

like when open adress ending .php auto redirected same adress ending of .html want.

when remove these lines:

rewriteengine on  errordocument 404 /page-404.html  

and try open non-existing directory got 404 error redirected page want. problem comes when add additional lines shown in first code posted.

where problem , why 404 error redirection not working in first example ?

thanks in advance!

have rules this:

errordocument 404 /page-404.html rewriteengine on  rewritecond %{the_request} ^[a-z]+\s([^\s]+)\.php\s [nc] rewriterule .* %1.html [r=301,l]  # make sure .php file exists requested .html file rewritecond %{document_root}/$1\.php -f [nc] rewriterule ^(.+?)\.html$ $1.php [l,nc]