Roman army

[Mediteran]

hi, i was wondering if anyone could help me concerning the roman army...

Historically, did the mix different legions for one army?

for example, i have legio X etruria and legio V apulia, now would they have both in one army or were they in separate armies, and each army only had legions from that specific place? and, did they mix "their" units (like hastati, triarii and so) with the others like hastati samnici and so?

and also abour retraining, or replenishing the legions, were they "retrained", and if they were, only at the specific place the legion is from or from anywhere?

sorry if my question is not understandable, english is not my native language :)

thanks!