So, am i able to do literally EVERYTHING that i want in a LD?

Is being a... infected (but not me, someone else) possible in a lucid dream?
And is everything authentic, or can i only dream and be what I already "encountered".
Sorry, in my opinion the title says everything.

The limit of what you can do in your dreams depends on your imagination and your belief.

Imagine the best circumstances for lucid dreaming, you are perfectly aware and the dream is perfectly stable and vivid.

So it basically feels like physical reality. This is in a way how it would feel to be plugged in to the Matrix. Now it all comes down to what you believe and what you can imagine, however you don't need to perfectly be able to visualize something because there is something that fills in the gap. But if you don't believe that you can for example fly, well then you wont be able to fly.

The Matrix, Jump Program - YouTube

"No one has every made the first jump"

It will take practise for you to be able to control the dream in this manner, but there are tricks of how to make it easier. For example have you seen the movie click?
Expect a control like that to be in your pocket and then try to put the same amount of trust that Adam Sandler does in the movie and BAM you have both the expecation and belief literally in your hands.

When you summon people by yourself, at least in my experience they don't turn out perfect very often. However if I explore the world and let the dream summon the people I meet, then they look normal, so I am more of an explorer than a controler which can be nice to.

But I hope that the answer helped you.

Yes, you can do anything you want, if you have control, that is. Everything bit of information that has passed through your senses – be it visual, auditory, tactile, smell or taste or even just thought – will possibly manifest in your dreams. In a sense, you can only dream of what you know. But all those things can be combined to create new things and places and people based on what you experienced through your senses.

There are other possibilities such as precognitive dreams, etc., but I'd rather not delve into that here. :)

Good luck!

As a beginner, I do not usually have full control. For example, in my last lucid I was able to use telekinesis very effectively, but I couldn't for the life of me conjure electricity. Mastermind's comparison with the Matrix Jump Program is spot on.

Well it takes a lot of practice to take complete control of your dream.

You can do anything you can imagine, and more. Whether or not you can do it reliably is the real issue. Sometimes the dream does not cooperate. Things rarely happen exactly as you expect. There is always a bit of unpredictability with dreams.