Not sure if this would be a mod or a cheat. Suggest you check out gtawiki where they have comprehensive sections on modifications and for cheats:
gta.wikia.com
A police outfit is not available to Niko in GTA IV. I do not know if there is a mod available on download via a computer, but I have not heard of one. You could check this out via some of the GTA dedicated sites, like gtawiki
There is no police suit in GTA IV in ordinary play. I do not know if there is a cheat or a modd (which would be more likely).
The answer is No. As of right now there is only a limited amount of disguises that Niko is able to wear, and a Police uniform is not one of those.
You can't. but u can get a nurse outfit a biker outfit a gta 3 outfit and a Statue of Liberty top. BUT U CANT GET COP OUTFIT.
There is a police station near to the Malibu Club. Enter the Station, and turn left in the locker room and there you will find the police outfit.
it is a mod for PC only you can go to
GTA4-Mods.com
only if you mod the PC version
The police Station where you get uniform is Washington Beach Police Station.Its is in front of the cross roads near the Malibu club.The uniform is in changing room.
The police uniform is at the police station near the bridge.You find that police station while going forward from the road in front of Malibu club.The uniform is in the bathroom on the left when you enter in the police station.
You can't, unless there is a mod or a cheat for one.
No there isn't.
No
get 100% progress with millie in the third city/las veagus
You can't, its a mod.
Yes if you type i like dressing up several times then you might get a luck that you find yourself in a army uniform.But you can download the army uniform to your skin files and then use it.
You can't.
You need the police uniform from Washington Beach Police Station. It'll be there when you complete mission Cop Land.
Walk through the door
You can't. You can be a good bystander though!