mod_rewrite help for php to html redirect, html to php intern, and support subdomains - .htaccess

Question

I want to always show .html in the address bar. All .php requests to be redirected to a .html in the address bar. And .html requests to show the .php file.
I have set up my webhoster with following domain and subdomains
www.example.com => /
test1.example.com => /test1
test2.example.com = /test2
Then I setup .htaccess in the root directory as
RewriteEngine on
# Externally redirect .php requests to .html
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteRule ^(.+)\.php$ /$1.html [R=302,L]
# Internally redirect .html requests to .php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)\.html$ $1.php [NC,QSA,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+).htm$ $1.php [NC,QSA,L]
This works great
www.example.com => /index.php
www.example.com/abc/def/test.php => /abc/def/test.php - Address bar shows "www.example.com/abc/def/test.html"
www.example.com/abc/def/test.html => /abc/def/test.php
but not for the subdomain
test1.example.com => /test1/index.php
test1.example.com/abc/def/test.html => /test1/abc/def/test.php
(!!) test1.example.com/abc/def/test.php => 404 - Address bar shows "test1.example.com/test1/abc/def/test.html"
For some reason test1 shows double. What lines do I need to change/add in the htaccess?