Yes, as long as they are both oil based or both water based.
Yes you can.
No and yes it depends
Superglue is a specific chemical, cyanoacryllate. It is the same in all brands of superglue, and therefore does not react when you mix different brands.
Yes you can mix different brands but I recommend you do not mix different weights. You can even mix synthetic oil with conventional oil. But as the weight of the oil is critical, do not ever mix one weight of oil with another, no matter if it is synthetic or conventional oil.
Mixing brands of power steering fuel does not make a difference. Just be sure to not mix different types of fuels.
Yes, different brands of dog food are ok to mix
I have two gallon of paint. Same brand name. one is egg shell the other is flat. can I mix the to together? ANSWER: As long as they are the same base, water or oil, you can mix them together. Realize though, that you will never be able to get touch up for the paint once it runs out unless you mix to a ratio that can be recreated.
Yes, mixing different brands of plumbing supplies is not a problem at all. Be sure to double check dimensions if you plan to mix and match parts, but there is no reason why you cannot do this.
different colours of paint
Sure. You can mix them. Why would you? It will not help prime the walls or wood. The primer coat needs to be applied separately to be effective.
I'm guessing this is auto paint. The best rule is to use a reducer of same brand some are not compatible with other brands. e.g.(PPG paint PPG reducer & activator). You will most likely have issues if you mix and match brands. And yes urethane reducer can be used with urethane paint.
Yes, it is fine to mix brands.