I got my answers! Thanks guys.

@sgunhouse Great! As far as I know Chromium browser is an open source project but Opera isn't! Why? Any license point for that...

@jimunderscorep Hmmm, upstream update! But [1.]Does it work for major releases? I think I found a instruction to add the repository 2 days ago, At that time I just wanted to test Opera and now I think It's really cool! Is there any official instruction from Opera team to add an rpm-based repository on my Fedora? It'll be pretty easy if it's a Copr repo! On the other hand [2.]Do the Opera developers team keep update this repository as soon as possible!?>A RETARDY QUESTION, SORRY! Since I saw that the GPG fingerprint is for 2017!

Edit 1: Afterall if there is no problem with the built-in update mechanism The color of opera icon at the top left corner, as you said for all kind of update and releases, I'd rather to go on this way instead of adding new repository. [3.]Is there any problem in this case?

Edit 2: Now I searched for the possible ways on this matter and found this page but it's for opera 12.10 and I am using Opera 52.0, [4.]Does this way work on my F28 and O52 properly?

Edit 3: Tada!!! I found the official instruction from opera website but I also found that a new disabled repository file added in /etc/yum.repos.d/ named "opera.repo" when I installed that rpm package thus there is no need to follow that instruction! If I want to enable repository, first simply add the GPG-key by sudo rpm --import https://rpm.opera.com/rpmrepo.key and then enabling the repository file. [5.]Is it right?
Wait! [6.]How about my currently installed Opera? Does it match with my Opera or I should reinstall opera from that repository!? I've configure and added some extension to Opera and I don't want to loose my configurations, so It will be good if it can be match with repository and no need to reinstall. Which one will happen?

Edit 4: [7.] And my last and unrelated question! Is Opera-browser based on Chromium!? I think saw something about this!

P S. Actually I prefer to don't add any extra repository, so because of this I am looking for an built-in update!
P S. Questions 1, 2, 3, 4, 6 Removed Because I found when I instaleed that rpm package it is also installed and enabled a repo for that!
Also I am so sorry about spams!

@jimunderscorep Hmmm, upstream update! But does it work for major release? I think I found a instruction to add the repository 2 days ago, At that time I just wanted to test Opera and now I think It's really cool! Is there any official instruction from Opera team to add an rpm-based repository on my Fedora? (It'll be pretty easy if it's a Copr repo!). On the other hand Do the Opera developers team keep update this repository as soon as possible!?(Mabe this is an idiot question XD sorry!)
Afterall if there is no problem with the built-in update mechanism (The color of opera icon at the top left corner, as you said) for all kind of update and releases, I'd rather to go on this way instead of adding new repository. Is there any problem in this case?

Hi there.
I downloaded Opera-stable-52...-amd64.rpm and installed on my Fedora 28 successfully. The mater that I opened this topic is How can I Keep update Opera while I didn't enable any repository for opera-browser! Is there any built-in update mechanism in Opera?
Thus how can I keep update Opera-stable when the developers team release the new update of browser?