Do integrated resistors in a LED make you work with an specific power source?

Hello, everyone! Totally new here.Well, I'm going to buy a pair of 12 volt "eagle eye" LED for a medicine experiment, and I planned to connect them to either a rectangular 9 volt battery or 3 cylindrical 3.7 volt batteries. But now, these LEDs are meant to be connected to a 12 volt car battery. Does the difference of the amperes between each power source (car battery, rectangular and cylindrical) conflict with the LED's functionality, or does the integrated resistor allow me to use any power source without trouble?Here's a picture of said PCB with the integrated resistor, for example (found on the internet), it just reads "300" and I don't know what that means. Sorry if all these questions and doubts are really silly, but again I'm a medicine student trying to make this work and electricity is a really complex world. Thanks in advance, wise people!!!

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How to wire a lamp with two switches and one power feed?

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Find Lost Password Windows 7?

My parent left the home for a couple of weeks (trip) and turned out to forget their login password of Windows 7 PCs. They asked me if possible to find the password? Need your opinion on this.

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