Suggest Me Open Source Content management system with these features

Suggest Me Open Source Content management system, feature with

Unlimited Page/Form Feedback/Menu
Form generator,
Sitemap Generator
Custom Title/Keyword/Desc
Editable Menus
Permissions to limit access to certain users
Picture/File Upload
Product Gallery/Portfolio
Easy to add custom webdesign templates.
easy to create/edit/update/delete content

Search Engine Friendly URLs with mod_rewrite

and must be not able to find script platform by any cms detector.
like: joomla,wordpress,drupal…

Did you look in this thread? That lists a number of the packages available and breaks it down by programming language, so you can find one that will run on your server.

Explore them (a large number have demo sites available). Find one that has the features you like and go with that one.

I would suggest what Dave mentioned above however your last criteria is going to be troublesome… Anyone familiar with a CMS will be able to figure out what you’re using based on the file system structure. If you want it to look like a custom CMS, you’re going to have to build a custom CMS. Otherwise I’m sure will figure out what you’re using.