where can I download library file: "Trade.mqh" for mql4?
can I use the mql5 version of that file for mql4?
I have that in metatrader5 but no in metatrader4 libraries.
no, you cant use the mt5 version. You can try to rewrite it, but it will be a lot different because of the different position mechanism of MT4 and MT5.
Maybe metaquotes will come up with something, try to ask them.