If I Uninstall/delete My Whatsapp App And Reinstall Will The Status Reset Itself

What will happen if I delete my whatsapp account & uninstall it? Will my old messages be back when I reinstall?

When you only uninstall your WhatsApp application from your phone without deleting your account than you can get your old messages and all media if you have a backup. Otherwise if you delete your account and install the app again then you won't get your old messages and the media. So, it's good to back up all your messages in your phone or by linking it with Google Drive. Google Drive will sync all your text messages and the media and you will be able to get it anytime.

I deleted my WhatsApp. If I reinstall once again, can I be able to see my old messages and pics which I sent and received before?

Yes of course if you had not deleted database of your previous WhatsApp. Of so then while reinstalling it will ask you to restore backup. And as soon as WhatsApp detected previous messages it will reinstall

If I reset my phone will I be exited from all groups in whats app?

Not really.Your WhatsApp backs up everyday either to Google drive or to your storage (you'll be asked to do enable it). The account will be removed when you reset your phone and so does the storage will be erased. Before you click on the reset, you'll be asked for backup options which even includes the WhatsApp database.So even if you reset your phone, you'll not be removed from other groups but your previous messages will be lost (If no backup file exists in your phone).

What will happen to the blocked contacts in WhatsApp when I change my mobile? Will they still be blocked?

When you delete your account, your state of phone goes back to whatever it was before the installation of whatsapp. So, I don't understand what do you mean by "what happens to blocked contacts on my Whatsapp?". Everything is gone, your whatsapp contacts itself are gone, the settings for each contact and the history. Whatsapp stores its data on your phone locally so if you uninstall and re-install whtasapp, you can retrieve previous data. But, deleting account is an irreversible process, the local whatsapp data of your phone will be deleted and even if you install whatsapp again, you won't be able to retrieve the old data. You will not be visible to your contacts next time they come online and their contact list is refreshed as you are gone from whatsapp. They will only have your previous conversation on the phone until they delete the chat. And even if they sent you a message after you have deleted your account, where will it go ? So, there is no separate case of what happens to blocked contacts if you delete your account as history of whatsapp from your phone is gone so no one is blocked or unblocked as there are no whatsapp contacts in the first place.