Also just to add up, lot of trips are twin sharing. but what if i want to do solo trip and it's not mentioned in the trip. so that trip might be only for twin sharing right ? and can not be redeemed for one person ?
No, you can redeem for one person. You only need to pay for yourself not for other person. Twin sharing is available just in case if you want to take some along otherwise you can travel solo, they will not ask you to pay for second person