There are no hidden uogrades ...
Upgrade center may upgrade HP of defence structures ,max amount of mana for turrets \ units ,research EMP weapons,Critical hit
Now about building upgrades:
Barracks>
1)Sniper Center
2)Teslaman
3)Command Center> //Main Upgrade
1)Machinegun
2)Firethrower
3)GENERAL C.C. > //(needed for tanks//Main Upgrade
1)Grenader center //(need for most of buildings)
//^^^^^^ Main upgrade
2)Engeneer center //(also neded for "Central")
3)Special Units
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Factory:
Factory level1>
1)Scouts
2)Spider-bombs > 1.1)(sorry forget name)
3)Factory lvl2 > //Main upgrade
1)EMP machinery
2)Artillery Machinery >2.1)
3)factory lvl3> //Main upgrade
1)APC tanks>Firethrower tanks
2)Destroyers
3)Rocket destroyers
1.1)Spider-bomb lvl2>
1.2)Spider-bomb upgrade3>
1.3)Hi-tech center
2.1.1)SCUD LAUNCHER
2.1.2)Blizzard Rocket Launcher
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Special buildings need:
Central>
1)Hi-Tech
2)Grenader
Hacking center> (upgrade of an "upgrade center")
1)central
2)Engineer
Black hawk(Helipad),water units.other stuff>
1)Factory lvl3
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About the hints. They of course could be turned of personally> 1 player turn off,other 9 players may see them
)
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P.S. i tested that version after your "bug" . nothing have been seemed everything the same as at russian version