A71 don't have double tab Screen lock feature and I don't want to install 3rd party apps because of virus content can you suggest me which app should I install for Screen clock.
There is no official settings or option to enable this feature in any of Samsung devices..you can use one hand operation+ to lock your device or use Accessibility>interaction and dexterity>assistant menu or if your device supports GoodLock app/NavStar then use that..
