Selling products using my Brand Name without any authorization

Since you trademark application has been filed only 2-3 days back that means that the application is pending before the Registrar of Trademark and your mark has not been registered. If a mark is not registered, then infringement cannot be claimed against another party but passing off can be claimed. So you can send a notice to the other party for passing off their goods as yours. However one of the precondition for passing off is that you should be a prior user then the party to whom you are sending the notice. Also goodwill and reputation of the mark is so importance in passing off.

No, you cannot claim the ownership under trademark act for infringement of your right and tradmark till you get the registration number. But you can sue and sent a legal notice to other party for passing off on the basis of your popularity and the date of use of your trademark. That you are a prior user of said brandname and the said brand name is you synonim.

Yes. The notice will be for "passing-off" and not "infringement" since your application is still pending. What is critical is that you have been using the mark before the other party. Consult a lawyer asap.