So “revisions” are a funny thing on Fiverr. You won’t waste a revision if they can’t open the file because it’s not like Fiverr closes the order after the buyer requests a revision. A buyer can constantly ask for modifications to be made and it’s up to the seller to put their foot down and say “no, you got your revision, no more.” It’s one of the ways Fiverr sort of intimidates sellers into providing more work for pushy buyers – big red Xs and “rejected” and “late” and constant little reminders “Don’t bother reading this message, get to work! Deliver on time! Go! Go!” that make new sellers work for nothing. So there’s no such thing as wasting revisions – you create and hand them out as you like.
Delivering in messages means you’ve given them the work and the order hasn’t even been marked as completed. The buyer can just walk away, cancel the order for no reason, or start heckling your work until you agree to cancel… then they use your work without permission.
Instead, deliver with the appropriate delivery method. If they can’t open it, they’ll tell you and then you tell them it won’t waste a revision. But don’t tell the buyer they may not be able to open it! They may use this as a means to cancel the order and use your work anyway. I’ve seen other sellers discuss this on the forum. Seller does work, buyer claims they can’t open it, buyer cancels. It could be that the buyer is incompetent, sure, but it seems likely that buyers would take advantage in this way, especially with new sellers.
If you want to check that your buyer can open the file, don’t send the delivery, send the same file type of something else as a tester (in fact, if you do this gig frequently, having a tester file for this purpose is a great idea). That can be sent on messages and the buyer can confirm they can open the file. You can even do this at the beginning of an order, so if a buyer can’t open the file type you can cancel the order immediately (before doing the work) or you can find another file type or other solution.