Spoilers

Finished the game yet I have some questions.

1.) I have read the good ending where all 3 factions are still alive, brotherhood , railroad and minutemen. Can someone help me out on this please ?

2.) If you choose institute, you get the institute white paint right ? Does this only apply to X01 power armor, all power armors ? Can the heavy combat armor be painted as well ?

3.) Where to find a heavy combat armor right arm ?

4.) How to find the black brotherhood of steel uniform , don't want to kill any BOS? Can you steal the uniform ? Or does the stealing perk with equipped items also means apparel ?

This should be moved to the spoilers forum, but I'll answer it here:

1. Siding with the Minutemen lets you go through the main quest without destroying any factions except for the Institute. If you build the Relay with Sturges and complete the Old Guns quest for the Minutemen, their path to the Nuclear Option is available. You can optionally destroy the Brotherhood after the main quest, too.

2. Yes to white Institute paint, yes it can only be applied to X-01, and I don't think it can be applied to any Combat Armor.

3. No clue, but they start appearing on enemies randomly as you level up.

4. The only one wearing it I think is Paladin Brandis - the last rank of Pickpocket will let you steal equipped apparel, but otherwise you'll have to kill him for it.