I lost my Keystore used to sign my apk. I wanted to update the app then I know this is not possible to update without the key. Now I want to unpublish the app and re-upload the apk with a different package name and keystore. Is It Possible to re-upload in google play store? if not please give me suggestions.
Yes, you can delete the previous application and re-upload it. You won't be able to use the same package name though, as it will already be taken by your old app. Simply re-upload it as you would when you want to publish a new app.
But remember, you should always keep your keystore and passwords saved!