Don't over think this.
If you know somebody who already makes sour dough, they need to refresh their culture once or twice a month. Get their "throw away" starter and use it to start yours. I bought a starter from King Arthur about 10 years ago. Still using the same starter today. King Arthur still sells sourdough starter. Their crocks work well too.
You can start a starter simply by putting out a bowl of water in the summer air. The yeast that's in the air will find its way into the water. You should then add some of that water to perhaps a half dozen jars of water flour mixture. Not every jar will start but the ones that start bubbling are worth keeping and nurturing. It may take a day or so at room temp before you see bubbles. After about two days the mixture will stop bubbling. That's when you need to add more flour/water mixture.
I use King Arthur unbleached bread flour in the light blue bag. Use 1 cup flour and one cup tap water and 1 cup starter. You can boil it if you want but I never do. Just make sure you don't add boiling water to the starter or you'll kill it. Tepid or lukewarm is fine. I don't worry about chlorine, add honey or lower the pH. If your water is unusually alkaline you may need to do something about it but first you would need to know if it's alkaline or acidic. Inexpensive pH test strips are available at pet stores that sell tropical fish, especially if they sell saltwater fish. Running your water through a carbon filter will remove the chlorine (Brita, PUR, ZeroWater). You can boil it too but then you have to wait for it to cool down. Simply leave the water in an open container and the chlorine will evaporate out...not sure how long that takes.
You'll need to repeat this a few times until you get a stable culture. Throw away one cup of starter mixture then add back one cup water and one cup flour that's been mixed together.
When you mix a fresh batch, leave it out on the counter for a few hours. It will double in size so make sure you have a big enough container. Starter over flows are a pain to clean up. From there, put your covered starter in the fridge for 2 or 3 weeks and then rebuild your starter again. I go 4 weeks maximum. Always put a date on the jar so you know when to do the refresh. Starter is like a pet, you have to take care of it and it's a long term commitment.
At 4 weeks, your starter will have a layer of black water on top. In general, don't worry about. The water will contain some alcohol as the yeast give it off as a by-product. When it's time to refresh, just pour off the layer of water. Give it a smell. It will have a sourdough smell. You'll quickly learn what that is. As far as I know I have never had a starter culture go bad. At one time I kept two cultures for white bread and one for rye. Now I just keep one culture for white bread.
When it's time to make your bread, grab 1 cup of starter for your bread and use the other cup to rebuild...one cup starter, one cup water, one cup fresh flour. Keep it simple.
You don't need added sugar for sourdough but some recipes may call for it. Authentic sourdough is much like authentic French baguettes...flour salt and water is all you really need. Baguettes use added yeast instead of the yeast in the starter. FYI, by French law, authentic French baguettes can only contain flour, salt, yeast and water, nothing else.
Over time, your starter, and your sourdough will develop their own special character/taste based on the yeast in your area.
Good luck!
When I was young and poor I baked all the bread my family of 5 ate, for several years. I baked yeast and sour dough breads with various flours.
So some hints: 1. Use good bread flour! King Arthur's or Hecker's brand, if those are not available look for a high gluten wheat flour, if possible unbleached.
2. Get good at making yeast breads first. Yeast is more efficient than lactoacid bacillus and will make bread rise better. Once you have made a few batches of nice home style white, then try adding in some different flours. I used to make oatmeal, rye and Anadamer bread. All of which are variations on white. None of them will rise as well due to the lack of gluten. Then add your sour dough to the yeast dough. Yes, you can get sourdough to rise without yeast but it will take much longer and occasionally fail. Adding the sour dough starter to a yeast dough will still get you the great sour flavor with the bonus of a better success rate.
3 There is no substitute for kneading. You generally can't stir enough flour into a dough to make a firm bread, you have to knead in the last couple cups. Your problem really sounds like not enough flour being kneaded in at the end. Your boule should be smooth and have a dusting of flour on the outside. You can over knead, if the dough starts to tear rather than stretch just let it rest for half an hour.
Best Answer
tl:dr; Do another batch.
It is not expected but not a full indication of a failure, but - There is a lot of colours in the picture which is suspicious. Also beyond vinegary after two days is suspicious. That kind of separation is indicative of the flour no longer having feed for their bacteria, which might explain the sour smell (not good).
What kind of environment did you leave it in? covered and cold?
I'd try another batch. It should smell nutty and just a tad sour. You might just have been unlucky with the dominating bugs in your starter.
Anecdotal: I have had long-lived primers separate a little bit and brought them back to life with some careful feeding.