How do I apply this new water based urethane over what I have been using for years?

I’ve removed several layers of paint and what I believe is shellac from 50 year old doors and trim. After stripper has fully dried I’ve sanded the wood surfaces, yet there is a gummy residue left on some areas of the wood surfaces. How do I remove this residue prior

A new house had the interior walls stained in a oil based stain. I think the stain was applied then rubbed off. It was a nice finish can you tell me how it was done?

I have a large room that has a wood beam ceiling that I hate. I would like to know what would be the easiest way to whitewash the ceiling. Could I just use a latex paint and paint it on and then rub it off? I can not tell if

I recently stained a new window with oil based maple color but don’t like the color. Like to make it darker. How do I do this?

Can I gel stain an interior six panel wood primed door from Lowes? They are cheaper to buy than the 6 panel pine ones.

I stained new wood in my home and over the past year the wood that was behind the pictures on the walls are now much lighter. How do I get the color to match again. I tried to restain the lighter spots that was behind the wall hangings this did

My windows are all stained golden oak but are turned black with condensation, what can I do with them?