Glancing through the documentation I didn't see anywhere that it states that a One-Time Purchase of a consumable product isn't an option, but I do use them in one of my channels. Users are able to purchase the same product again and again.
I'm not sure what you're asking. Within the channel/app, you just get whether or not the purchase succeeded from roChannelStore like any other purchase. I can get a history of transactions from https://developer.roku.com/transactions, but to be honest I don't really keep track of whether or not a user purchased a one-time consumable since the user can purchase the same thing over and over again.