would manjaro linux be considered under the arch linux forum ? Since its primarily arch with bells and whistles ?

Manjaro has a forum. Why not use them? I use Manjaro and never had an issue on the Manjaro forums.

No, you'll find that Manjaro isn't supported on the Arch Linux Forum, and Manjaro related threads get closed by the Arch admins quickly, so your best bet is to follow LinBox2013's suggestion and use the Manjaro Forum for questions relating to that distribution. Another option might be to post them here, on LinuxQuestions.

Why not install Arch if you like the Arch forums?

Thats the simplest solution. Keep in mind if you try to use any Arch related distro, and try to trick people on ArchBBS into supporting it, your ploy will be uncovered very quickly.

Just use Arch! Its fun.

Manjaro has a forum. If you want to ask questions about Manjaro use http://forum.manjaro.org. To get knowledge/information about Arch based distros you can refer Arch wiki.

The Arch folks (me excluded) are not dummies and they don't like "pretenders" much do the "hard" install and you'll be better off. The bigger reason Arch folks don't much like manjaro is they use there own repos that changes the complexion of Arch a great deal. Slackware has it's manual dependency resolution and build from source, Gentoo has the build everything, and Arch has it's manual install. These give character to the distro and set a certain bar to "weed out" folks.

Take your time follow the wiki and you're golden, then break stuff install again rinse and repeat until your Yoda. It always helps to write stuff down analog is always best.

Here are the links to the Arch wiki and the Arch bbs.

https://wiki.archlinux.org/
https://bbs.archlinux.org/

Unfortunately, you will have to sign up separately for each site as there is no single sign on supported at the Arch family of websites.

If you do indeed end up using Manjaro or Archbang or some other arch derivative, you can still extract some useful information from these sites to help you fix issues. A lot of the derivatives have a base Arch install with only some minor tweaks, so much of the documentation will work on them as well as standard Arch.

As mentioned by Germany_Chris and Enindu and myself, it isn't a good idea to request support for those distro's on the actual Arch forums. Request any support at the related site.

I really like Arch. Arch has superb package manager called Pacman. Love Pacman. But I still have doubt, can I install Arch successfully on my machine? What if I can't? [I still want to do it.] That's why I'm now using this Pacman based distro called Manjaro. Manjaro seems good to me. Manjaro is like a user friendly version of Arch linux. I don't telling you to use Manjaro. Choose wisely. Arch is the 1st choice and Manjaro is 2nd one for me.

But anyway, don't ask questions about Manjaro in Arch forums. That's totally stupid.

Because Manjaro is not Arch, there even further from Arch than Archbang as they use there own Repo's. Manjaro is to Arch what Ubuntu is to Debian. To be honest you have to have a certain personality type to like the Arch forums anyway.

Trying to get help with Manjaro on the Arch forums would be a bad idea based on how they act if you try and get help with that distro in the IRC chat. Manjaro isn't even Arch anyways, as it uses its own repos. Basically, if you want Arch, install it the Arch Way, I'll link the Beginners' Guide and the ISO, or if you wanna keep Manjaro, get help from the Manjaro forums and the Manjaro IRC.

Arch Beginners' Guide: https://wiki.archlinux.org/index.php/Beginners%27_guide
Arch ISO:https://www.archlinux.org/download/