Use Magic Device requires a DC Check of 15 + spell level to successfully use a wand. If you do not succeed in your check, a charge is not expended. Some DM-only loot may not work this way.

Scroll use with UMD requires a check of 25 + spell level of scroll, scroll is not lost if you fail.

These are the modifications made to UMD, so my question is whether UMD still functions the same with regards to what equipment you can equip (ie weapons, armor) by putting ranks into it?

Yes, though some equipment you will find in game (very specialized) we have put restrictions on. Those you will know by the *Only wear if X, do not use UMD to use this device*. These things are usually boots, armor, etc, that are very class specialized and that we would like to keep that way.

Other than that, everything is fair game.