Is there any way to find which commands have been executed between 2 specific dates (like 2 to 3 months period)?
I can use the history command, but I have powered the system on/off.
Is this possible? And how?
Not by default. You should install the psacct (Process Accounting) utilities to get this functionality.
The ubuntu package turns on process accounting as part of the install. It provides the following commands:
No, not possible with the default install. If you care about the next 2 - 3 months, it is possible to set something up to track this, but not for the prior 2-3 months.