There are two periods in PA, one is GL Period and other is PA period
you can decide whether to manitain common periods between GL and PA ( It is a check box in Projects Implementation options)
Incase you set it as common, then whatever calendar is defined in GL will appear in GL period form and also in PA period window
Copy from GL button in PA period form resembles to copy the periods defined in the GL to PA period ( for example: the GL calendar is defined say till end of 2013, you have copied to PA period, so PA period also has till end of 2013) after a while GL team adds the calendar periods for 2014, when you click on copy from GL, then copies remaning periods that weren't copied earlier
Check box Reporting period is something which you set to make sure all your Project status Inquiry details, reporting details are considered
for example: you have set March 2013, then when you run PRC: update project summary amounts then updates all the project details till the period of March-2013
When you setup Maintain Common PA and GL periods in Projects you will get the definition of periods shared for PA periods and GL periods. That means, if you have GL periods as Months and the start date and end date of GL periods meet the calendar dates, you will get the same period definitions as PA periods. The copy functionality copies the period definitions (period names and date boundaries) and not the period statuses.
When you use such setup you will not be able to use monthly periods in GL and weekly periods as PA periods.
Note you need to maintain the status of the period in PA, and separately maintain the status of the period in GL. Assuming you open period March 2013 in GL, it will be opened for all subledgers like, PO, AP, AR, PA, etc. When you are closing that period in PA, no new transactions could be accounted as of March in PA. However, GL may still be open, so you would be able to enter journal entries directly to GL for the month of March-2013.
I think Dina already answered your concern: "Note you need to maintain the status of the period in PA, and separately maintain the status of the period in GL. Assuming you open period March 2013 in GL, it will be opened for all subledgers like, PO, AP, AR, PA, etc. "
Your PA period was opened when you opened your GL period.
If that's not the question you have outstanding please restate what it is you require an answer for.