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You can log into previous years to look at previous T4s. When you're selecting your company (or you can go to File > Select Company), select the previous year and log in. 

When generating the Employee History Summary Journal to review my totals, why do I need to select the date range to include paycards based on the pay date and not the pay period ending date?

Your T4s are based on the pay date - meaning it will include values for pay periods which pay dates are in the current year. You should be generating the Employee History 

II. Creating T4s, T4As, and RL-1s 

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