Hi, I will try to answer your many questions into one.
I have been working as a Game tester for over 1 year and let me tell you it's one of the most comfortable jobs I have but also stressful jobs I have had. Let me explain, so your in a laboratory and you have a screen in front of you with a game that your testing, you probably have never heard of the game because it's not out yet, but more importantly it's a game your going to be "testing" not "playing". A lot of people think that because your a game tester, you sit on a chair for 8 hours and get paid to just play the game and break it. Unfortunately your not the only "breaking" that someone does is in compliance and to work there you need to know a lot about coding and probably a degree or previous experience or work your way up to that department.
You are a User interactions tester, meaning you making sure that what players experience is what you would want to experience. For instance if you see that the text on the game doesn't localize correctly then you let someone know and they write it down on and if it's a serious issue you get the game back again with the corrected language that you saw.
Simple things like this is what you would be initially be looking for on a day to day basis. However this isn't what your being contracted to do as part of job. Your actual job is to follow out what is known as FTC (Functional Test Case). These are scenarios that Microsoft have seen over the following years of development occur on regular basis and they are protocol for the company you would be working for to carry out. An example would be to, make sure a chat pad works for the xbox controller on the game, can you use the chatpad in the game, does it have negative effect in the game. These tests can number from 20-100 a day which you would eventually remember by the sheer amount of times of repetition.
That's the Game Tester job role.
Where you can become a games tester is a bit difficult because there are few and far.
are the two that I know, from these companies you could venture onto something else and work for Ubisoft or EA but the likelyness of that is very slim. But not impossible.
I hope this is what you wanted to hear and everything you need to know.
Oh I had no previous experience and there are no minimum requirements to become a tester, no qualifications unless you want to break games with codes.
Good luck with it all!