If you bought a ticket for (say) $400 for 2 people and cancel the trip, you’ll get a voucher for $400. You can use it however you want, either for 1, 2, 3, or more.
Most e-vouchers are good to be used many times until used up, but some are one-time use only, (Using the above example, if it was one-time use and you bought a $25 ticket, you would lose the remaining $375 value. If it was the other kind, you would get a new voucher for $375.)
Certainly note the rules on the specific voucher YOU have in hand. Just yesterday I used a voucher that a) could only be used by me, not transferred to someone else, b) had to be used on only one reservation (if that ticket cost less than the voucher, the remaining value of the voucher would be lost), and c) had an expiration date. YMMV--do look carefully at YOUR voucher's terms.
As I said previously, most e-vouchers are good until fully used. I have received many of these. However, recently I cancelled a saver fare ticket under the current exemptions. The e-voucher I received was the one-time use that I mentioned above!
While it was only for under $20, it is very easy for me to use it all at once. But if I did not notice this restriction before I used it, or if it was for $300 or $800 and I only bought a new ticket for $58, I might be mad!
It should not. But it would be issued to the person who actually PAID for the ticket (which may or may not be the one traveling). However, (unless there are restrictions placed on it), that voucher can be used by that person to purchase a ticket in the name of ANYONE!
Its been a long time, and not directly related to the OP's question, but the one-use-only voucher I have gotten were for a courtesy (good will) refund. Given, like, if you complained that your mash potatoes were too lumpy.
The one I received last month was due to a cancellation of a saver fare ticket - which is not normally refundable but due to COVID-19 is. This was a one-time use voucher. If I had a value fare ticket, the voucher would have been the “use until gone” type.
I guess, and I emphasise guess, that it depends on the voucher. Does the voucher just have a monetary value to be redeemed against future trips, or is it a point to point voucher simply to move the original trip to a new date of your choosing?
Maybe the "open sleeper" part of the second option would be lost, as that can surely only be valid if two travel?