Hello Edu,
if you place the updated EA with the same magic number, it should take control over the opened trade, because it will recognize it as its own.
Same when you disconnect the Meta Trader, or restart the computer, the EAs recognize after that the opened trades with the magic numbers.
and please, how many times should i try the montecarlo validation? Because i have seen that if i try multiple times: sometimes the Ea pass and others times not
This is because the Monte Carlo runs every time different simulations, but with in the options you have selected. For example, if you run 3 and 2 pass is fine, or 3 out of 5. It really depends on the results you see.
Also, if you have 20 tests, I consider it as a good result if more than 15 pass.