If you want to change or upgrade AWS instance type/hardware, you can do that anytime by following the steps, you can change your t2.micro instance to m3.medium and change the storage size too.
Follow this link to learn how to create an instance.
Changing your instance type
#1 Login to your AWS Console
#2 Go to EC2 > Instances
#3 From there right click the instance you want to change and stop it from Instance State > Stop (there will be a downtime).
#4 Right click the instance again and choose 'Change Instance Type' from the Instance Settings
#5 Now you will be able to choose different type 'hardware/configuration' and click on apply.
#Start the instance again and now the VM will be running with the new settings.