To tenderize, try poking a bunch of tiny holes in the meat. "Pounding" can bruise the meat and make it worse.
We obviously will recommend to prepare meat when it's fresh, but freezing is very common and does not affect the flavour of the meat. Meat will keep in the freezer up to a year as long as it was frozen while still fresh, and has been frozen solid for the duration. Re-freezing meat is a no-no.
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