Of course, you can always send a Newsletter, or an Update with free download links, to all previous buyers of a product, but I gather you only want buyers before a certain date to receive the offer.
If the first version was a separate product (i.e., you created a new product in Seller Admin for later versions), that should have its own Buyer Group that you can send to, if the product hasn't been deleted. Even so, we may be able to undelete the product for you temporarily if it can be clearly identified.
Otherwise, if you've just been editing the same product to upload replacement files for the latest versions, email our Support team with the item name/number of the product and the cut-off date when newer buyers would be ineligible for the update, along with your E-junkie password:
We can export a copy of your Buyer Group list for the product, remove buyers before the cut-off date, and re-import the remainder of that list to a dummy product that you can select to receive an Update or Newsletter. If you don't want to issue free links in an Update, you can just send a Newsletter with a discount code, purchase link, and/or link to a product page where they can order.