1. my usb disk is bootable ?
Boot your Mac using the external disk and verify you can do this. Boot holding the "Option" key and you should get a list of all the bootable disks and/or partitions available. Select the external disk. If your external disk is not listed, then your approach did not work as desired.
2. if OSX was damaged, I can use usb disk to restore the whole OSX (included app+data) to original disk?
Yes. The state of your Mac will be consistent with when you last updated the clone. You would boot from the clone and use Carbon Copy Cloner to transfer the data back to the internal boot disk.
3. You think it's better to create OSX image for my scope?
I do not understand this question. Making a wild guess, I'm wondering if you think my reference to Disk Utility was suggesting you make a disk image. I was not. The Disk Utility -> Restore feature basically does the same kind of work Carbon Copy Cloner or SuperDuper perform, with much fewer bells and whistles. For example, you cannot incrementally update your clone with Disk Utility, which means any update requires copying everything, even if it has not changed. You cannot schedule Disk Utility to perform the copy. You have to manually run Disk Utility -> Restore each time. Carbon Copy Cloner and SuperDuper offer incremental updates of the clone, copying only the files which have changed, and both offer the ability to schedule the update, so it happens on a regular bases.
If my guess as to what your #3 question was about is wrong, then you need to restate the question.