Yes read and search forum, asking questions like this gets you into lazy mindset that will traverse over to your growing and ultimately ending in problems. The more you learn, apply, try and learn will help you think on your own and correct issues more efficiently.
To your questions...
Water should be to bottom or slightly below your net pot. I run mine at bottom entire grow some others run the water inch or two below it.
Changing is preference, I change every two three weeks, some do it every week. This is where the thinking comes in, try it one way then another and use what works for your grow.
Ph should be 5.6 to 6.2 ish. I keep mine at 5.9 to 6 most of the time. Use a ph meter not test liquids.
Nutes is another multiple answer question, every manufacturer claims improved formulas etc.. They are all pretty much same to growers like you and myself. They all have different strengths issues etc... Try one and get the basics down then you can venture to try others. I suggest a all in one like dynagro or gh Lucas etc...
Make sure your starting water ppm is low if your not using RO water. Oh ya ppm meter is necessary too.
Growing is not just plant it forget it, it's a hobby that has a long learning curve if you want to be successful.
Good luck.
