Hotclutch

Dear  @peterbuzzin,  @MrPhil , @Hotclutch  
thank you very much for your help.
The RewriteRule :
RewriteEngine On 
RewriteBase /catalog/
RewriteRule !^admin($|/) https://www. newdomain.com%{REQUEST_URI} [L,R=301]
did the magic impeccably.  
The problem I had was that the other RewriteRule in the old domain (on the old hosting) they were interfering.
I deactivate the old RewriteRule and voilà!!!
Best regards.
Valqui

so how did you put it down in htaccess that it throws the error ?
I think it could be like this, but not 100% sure:
RewriteEngine On RewriteBase /catalog/ RewriteRule ^(.*)-p-(.*).html$ product_info.php?products_id=$2&%{QUERY_STRING} RewriteRule ^(.*)-c-(.*).html$ index.php?cPath=$2&%{QUERY_STRING} RewriteRule ^(.*)-m-([0-9]+).html$ index.php?manufacturers_id=$2&%{QUERY_STRING} RewriteRule ^(.*)-pi-([0-9]+).html$ popup_image.php?pID=$2&%{QUERY_STRING} RewriteRule ^(.*)-t-([0-9]+).html$ articles.php?tPath=$2&%{QUERY_STRING} RewriteRule ^(.*)-a-([0-9]+).html$ article_info.php?articles_id=$2&%{QUERY_STRING} RewriteRule ^(.*)-pr-([0-9]+).html$ product_reviews.php?products_id=$2&%{QUERY_STRING} RewriteRule ^(.*)-pri-([0-9]+).html$ product_reviews_info.php?products_id=$2&%{QUERY_STRING} RewriteRule ^(.*)-i-([0-9]+).html$ information.php?info_id=$2&%{QUERY_STRING} RewriteRule !^catalog/admin($|/) https://www.newdomain.com%{REQUEST_URI} [L,R=301] Rewrite ^(.*)$ https://www.newdomain.com/$1 [R=301,L]  

I see the addon was submitted under Ver 2.2, not sure if that was a mistake, but Neither Bootstrap nor official osC has a file called main_page.tpl.php
Also note that the bootstrap version removes these kind of definitions:
<?php require(DIR_WS_INCLUDES . 'cur_update.php'); ?> So you should use instead:
<?php require('includes/cur_update.php'); ?>  

Here is the demo of last official osC:
https://demo.oscommerce.com/product_info.php?products_id=28
You already have a small image gallery. The bootstrap code is the same as the last official osC in this respect.

It should be RewriteRule
Note those tags on the rule that MrPhil gave - and how i put it in my post above
Rewrite ^(.*)$ https://<www.newdomain.com>/$1 [R=301,L] Rewrite ^(.*)$ https://www.newdomain.com/$1 [R=301,L]  

I just checked what i wrote above - Rewrite - but it should be RewriteRule 

Does this rule work when you have it on its own - the one MrPhil gave ?
RewriteRule ^(.*)$ https://www.newdomain.com/$1 [R=301,L] Try to get that one to work first, then you can add the admin exclusion rule afterwards. 

Hang on ...
The rule that Pete gave excludes and redirects, so you only need that one rule. That one works confirm ?
Then you don't need to add anything else.

ok, then i advise you to turn it off, until somone can post the htaccess that you need. the rules are complex and can mess up your SEO.
 

change to
if ( !isset($params['type']) ) { $params = array('type' => ''); $params['type'] = 'submit'; } the addition is
$params = array('type' => '');  

This is part of the installation script, you don't need to be making changes here. After you install it is recommended to delete the install folder from your server, and that will be the last you need that file/folder.
 

categories.php
Find:
<tr> <td class="main"><?php if ($i == 0) echo TEXT_PRODUCTS_NAME; ?></td> <td class="main"><?php echo tep_image(tep_catalog_href_link('includes/languages/' . $languages[$i]['directory'] . '/images/' . $languages[$i]['image'], '', 'SSL'), $languages[$i]['name']) . '&nbsp;' . tep_draw_input_field('products_name[' . $languages[$i]['id'] . ']', (empty($pInfo->products_id) ? '' : tep_get_products_name($pInfo->products_id, $languages[$i]['id']))); ?></td> </tr> Replace with:
<tr> <td class="main"><?php if ($i == 0) echo TEXT_PRODUCTS_NAME; ?></td> <td class="main"><?php echo tep_image(tep_catalog_href_link('includes/languages/' . $languages[$i]['directory'] . '/images/' . $languages[$i]['image'], '', 'SSL'), $languages[$i]['name']) . '&nbsp;' . tep_draw_input_field('products_name[' . $languages[$i]['id'] . ']', (empty($pInfo->products_id) ? '' : tep_get_products_name($pInfo->products_id, $languages[$i]['id'])), 'style="width: 500px;"'); ?></td> </tr> Untested, but should work.

If you have any external links of value you will need to keep the old domain (as a parked domain) indefinitely. Otherwise you just need to wait for Google to crawl out the old site completely, this could take a few months to few years - this is because Google attaches a low priority to old junk URLs such as 404s and will only crawl these once a year or less.
^^ With that said, you might want to consider using a redirect at all. If you don't have much of a SEO position to protect, then this is a good opportunity to get rid of these old junk URLs like 404s, because with the redirect in place these will also be transferred.

I don't see why the CEs can't be given version numbers.
Just take the latest BS4 edge and label it anything, so that people can have a frame of reference.

The new domain will be considered a new site. If you own both domains then you can implement a 301 redirect of the old domain to the new, that will preserve most of the value built up by the old domain and transfer it onto the new domain.
fixed.

Free or Open Source ? 

Some people think they know SEO when actually they know nothing at all. So this is not true. I look at most osCommerce shops and see SEO mistakes, even after the webmaster thinks he/she has optimised their shop.

mt-2 may not be defined in Bootstrap 3, only 4.
so you can try adding this to your custom.css
.mt-2 {margin-top: 1rem}
then press ctrl+ f5 to see if that works.
 

Unique content is best, but supplier text is common amongst ecommerce sites. I don't see Google penalising sites for it. Even if you have this kind of product description you can still compete by exploiting the many other ranking factors.

It should be disabled. As to why, please read my posts i have already made, i don't want to repeat myself. You can use the module if are you able to modify it, so that it produces correct, and desired results.

^^ It's not that simple.
Using your site, of these 3 URLs
https://chilleddisplays.co.uk/product_info.php/products_id/2 https://chilleddisplays.co.uk/product_info.php/cPath/1_23/products_id/2
https://chilleddisplays.co.uk/product_info.php/manufacturers_id/1/products_id/2
What makes the 1st URL the best choice as canonical ?
There are many issues with the canonical tag module besides this.

Here is the support thread for USU5, but the original author is no longer active on the forum:
The original author's code:
https://apps.oscommerce.com/5GV7s&amp;ultimate-seo-urls-5-pro
There's also another updated version by another community member here:
https://apps.oscommerce.com/Hj4y0&amp;ultimate-seo-urls-5-for-responsive-oscom
 
Here is Chemo's support thread:
Chemo's ultimate SEO URLS is here:
https://apps.oscommerce.com/36rDo&amp;ultimate-seo-urls
Not sure if there may be another version people use.

Update on above
The author kindly PM'ed me and gave me a site to check with screaming frog, this was all ok, but it helps a lot to know it was my end
He suggested a Cache issue, but i had cleared the cache many times, but with fresh eyes i had discovered that the although the admin was clearing the cache there was still a file left
 
I manually deleted this in FTP and switched over to cache by file rather than sqlite and it appears to have done the trick, just finished a crawl and the issue has gone away
will keep an eye on the reset USU5 Cache to ensure it does actually do as it should, maybe the cache file was corrupted, but this version is running well
hope this helps someone
 
regards

There's always been only 1 way - Chemo's ultimate SEO URLs, and SEO URLS 5 by FWR Media.