I was wondering some questions about najasat hopefully you can give me an answer to

1. If a item that has become najjis by something that require for it to be washed more than once like pig, dog or urine, after lets say the first wash is the water that leaks off of it considered najjis if it doesnt change color? or only if it changes color?

2- If our hand becomes najjis by one of those things mentioned above and we slightly rubb them together under a tap is that suffice to say its been washed twice?

3. Is tap water connected to a kurr source considered only kurr water or flowing/running water as well?

4- I often find myself doubting after making something tahir. Because these doubts happen alot, I can just completely dismiss them right?

1. According to Sayyid Sistani all of the required washes, whether 2, 3 or 7, are mutanajjis (assuming it is being done with little water), irrespective of color.
2. Yes, as long as you have washed off the najasah
3. If the tap water is connected to a source that is Kurr then yes.
3. Yes, if you are kathir al-shak, someone who doubts a lot