How To Identify Specific Model of Dell Inspiron 15 3000 Series as well as HDD, RAM and Battery Compatibility

Hi! I own a Dell Inspiron 15 3000 Series. I have the following concerns:

1. System Information in PC as well as Service Tag entered in the Dell Support Website identifies my PC as 3542 but there is a sticker located under the laptop, to the right above the service tag sticker which appears xxxxx/xxxxx/2014 and then below this characters reads 3878. I just want to make sure because I am planning to upgrade my HDD and RAM and replace my battery and I don't want to encounter any compatibility issues. So what really is the model of my laptop?

2. Obviously depending on the confirmed model of my 15 3000 series, what is the compatible HDD (rpm, physical size, maximum GB/TB capacity, etc.), RAM (type, 1.35 or 1.5v, maximum GB capacity, etc.), and battery (type whether lithium ion or other, its model, 11.1V vs 14V, 64Wh vs other, etc.) 3542 or 3878 respectively.

Thank you very much to those who will help and I hope to get answers as soon as possible!