WhatsApp for iOS is getting a new group audio calls feature; this means that soon you will be able to make voice calls with your multiple contacts right from WhatsApp. The new change is apparently server-side roll out, so it might take some time for everyone to get this new feature.
On the other hand, WhatsApp for Android gets ‘Select all’ chats to perform quick actions. This will easily let you mark all the new messages as read or archive all your chats with a single tap. For the ‘select all’ option to appear in the menu, you will have to select one chat at least. For the feature to be present, Android users need to have version 2.18.60 or above. In case if you haven’t got the update, you will have to wait for next beta release.
As for the group audio calling on iOS, the interface is very similar to what we have seen for individual audio calls, but with multiple caller IDs. The U.I has buttons to enable speaker, video call, and mute button below the profile pictures of the participants. However, the limit participants for group audio calls hasn’t been revealed. The group audio calling functionality was announced back at the F8 event earlier this month.
Source 1, 2