www programming

if ((window.self !== window.top) != true) { //(or get loop)
// if(/adm\//ig.exec(window.location.href) === null){ // avoid x ACP
  var w3all_r = window.location.href.replace(/sid=.+/gi, '');
  w3all_r = w3all0Normalize_phpBBUrl(w3all_r);
  hrefEnc = window.btoa(unescape(encodeURIComponent(w3all_r)));
  href0 =  wordpress_url_page_f + '/?w3=' + hrefEnc;
  document.location.replace(href0);
}
//}
// END force w3all to iframe redirect
</script>

if( /\/adm\//ig.exec(href) !== null ){
e.preventDefault();
window.open(href,'_blank');
return;
}

Good point, you may have reason. By the way since more advanced users can find this easy and short to do, for some other it is maybe a pain in the a** if something goes wrong on some configuration. And it is commonly useful to have two tabs opened to check front end while operating on ACP.
To switch back and let load ACP into iframe, will be by the way just commenting out two lines in this way x overall_header code:
[code]if ((window.self !== window.top) != true) { //(or get loop)
// if(/adm\//ig.exec(window.location.href) === null){ // avoid x ACP
var w3all_r = window.location.href.replace(/sid=.+/gi, '');
w3all_r = w3all0Normalize_phpBBUrl(w3all_r);
hrefEnc = window.btoa(unescape(encodeURIComponent(w3all_r)));
href0 = wordpress_url_page_f + '/?w3=' + hrefEnc;
document.location.replace(href0);
}
//}
// END force w3all to iframe redirect
</script>[/code]
and into overall_footer code comment out or remove:
[code]if( /\/adm\//ig.exec(href) !== null ){
e.preventDefault();
window.open(href,'_blank');
return;
}[/code]
So this will be added into bottom iframe procedure (or as hints on inline code), with corrected hints on how to achieve the easy joke.

I understand the code change for direct access which means the crawlers will index those pages likewise if people know that they will be able to access the direct forum URL outside iFrame.

I think the previous code is fine and if access is needed to forum to fix simething then remove the overall_header.html code to allow access while fixing.

[size=130][b][url=https://www.axew3.com/w3/2018/12/phpbb-wordpress-template-integration-iframe-v3/]the overall_header.html and overall_footer.html v3 JS code has been patched[/url][/b][/size] because it was hard for all to access ACP when iframe activated, and for several other reasons:
now the code has been changed to:
when phpBB admin ACP link clicked, new page will be opened if clicked within iframe.
when acp page, login or ACP admin, accessed via direct url, equally, it will be opened as called, external, no redirect to iframe will fire.
That will make the situation more clear and useful for all.

the complete correct code has been published at date of this post, with new plugin 1.9.4 release.

This online installation example at date of this post run:
the [size=120]new [url=https://www.axew3.com/w3/2018/12/phpbb-wordpress-template-integration-iframe-v3/]v3 iframe code[/url] and phpBB 3.2.5.[/size]
Let check to resolve, in case, any possible remaining bug that by the way at moment seem to not come out in any way ;)

p.s beside all fixed in one shot about redirects of any kind, note that also inline posts links now loads without the "in iframe page reload" bad effect. Also this aspect has been definitively resolved.

Uh! let check this kind of links inline into a post:
https://www.axew3.com/w3/forums/viewforum.php?f=1

yeah, you have the same result! in any way you open it ...

you do not have to edit any phpBB notification email template to redirect users to iframe.
you do not have to edit htaccess.
you do not have to worry about spiders and seo.

The [b][i]overall_footer.html[/i] v3 code[/b] has been updated at date of this reply.
It fix a problem on redirect [i]same domain links[/i].
Now all should work smooth and perfect ...