How to stay Invisible on Whatsapp?

Whatsapp has the coolest feature of showing the exact time when you were online or last seen to your friends. But sometimes it becomes annoying as everyone knows about your last seen activity. So here is a post of mine " How to stay Invisible on Whatsapp".
Three things you can do with this:
1.) You can secretly read messages
2.) You can secretly send messages
3.) Your last seen will not show

How to do this?
-> very simple, for

1.) Whenever a message comes on whatsapp and you want to read but don't want to show that your have read their messages. Simply switch off your mobile data or any other Internet connection on your phone. Now open whatsapp and read the message which you want to read. Now close whatsapp and switch on your mobile data or wifi(if you are connected with wifi). In this way you can read the message secretly.

2.) Whenever a message comes on whatsapp and you want to reply to one of your friend and do not want to show your another friend that you are online. How to do it?
 It is very easy, just simply switch off your mobile data or any other Internet connection on your phone. Now open whatsapp and read the message which you want to read and reply to it. Now close whatsapp and switch on your mobile data or wifi(if you are connected with wifi).In this way your message will be secretly sent to your friend in the background and your another friend have no idea whether you came to whatsapp or not because you last seen status will not change.

3.) If you like to chat with one of your friend and avoid another friend without letting him/her know that you are actually online then simply repeat the above step. Simply switch off your mobile data or any other Internet connection on your phone. Reply to a friend whom you want to chat with then close whatsapp and switch on the mobile data and wifi(if you are connected with wifi). Repeat the process as many times your are sending the message. The message will be secretly delivered to your friend in the background. In this way you can chat with your friend without letting anyone know about it. As your last seen will not change.