You are making a mistake.
There are no browsers based on Chrome or Opera.
Browsers are based on a engine, not on another browser.
I believe it is a bad idea to allow extensions in the SafeZone Browser unless they have been checked by avast first.
If every extension simply would be allowed it means that also extensions with security issues (and malicious ones) can be installed and that would make the safety implementations of the browser basically useless.
I already find it a bad thing that it allows Flash.
Flash is very well known for the security flaws.
And besides that, Flash is history.
Adobe is not gonna develop it anymore and is abandoning it.
Several browser developers already have announced that there will be no flash support in future versions.
Things should be done within the HTML5 standard.