301 redirect htaccess and Nginx settings issues and .composer folder - redirect

Question

I've had some hit and miss results setting up htaccess to forward on a couple of aged domains I acquired to my main site. I wouldn't describe myself as advanced more an enthusiastic intermediate so a nudge in the right direction would be greatly appreciated. I've checked answers but nothing definitive that I can see that relates to my specific issue and the composer folder. In Apache/Nginx I have in directives (http/https)
RewriteEngine On
ErrorDocument 404 https://my-main-site.com/my-page-or-blog-post/
I have 'Restrict the ability to follow symbolic links' unchecked as I have reference to symlinks in htaccess and so avoids a 500 error. I also have put up a static html page so if anyone hits the old aged domain it's not an automatic redirect they'll see the static HTML page with reference to the old/aged domain. So the 301 is sort of in the background but I'm getting a 302 result. My htaccess looks like this......
Options +FollowSymLinks
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^old-site-aged-domain.com$ [NC]
RewriteRule ^(.*)$ https://my-main-site.com/my-page-or-blog-post/ [R=301,L]
However when I go in to AHREFS and look at the backlink data it's showing a 302, however it does confirm http>https is working fine.
http://www.old-site-aged-domain.com/info-page.html
301
https://www.old-site-aged-domain.com/info-page.html
302
https://my-main-site.com/my-page-or-blog-post/
In my site root I also have .composer folder (as well as error_docs, .ssh, httpdocs, logs, .revisium_antivirus_cache), I'm sort of aware what the purpose of this is (PHP) but there are 2 further htaccess files in there, the second smaller htaccess file only has 'deny from all' as content. I wonder if this folder with these 2 htaccess files is presenting a problem/conflict i.e. 3 x htaccess files. The smaller htaccess file is in .composer/cache. The larger htaccess file is in .composer. Should I delete these 2 x htaccess files in .composer folder.
Thanks in advance for any help
James
rewrote htaccess on numerous occasions but without success