Can I buy ticket for 12-25 year old when I am still under 26? There is no this info on the website I want to purchase from. It is Rhone express (Lyon, France)
As explained in the answers to this question, in France, as well as in other countries, you are the given age till your next birthday and you can buy and use that 12/25 year old ticket from your 12th birthday till your 26th birthday.
In some cases you can use a multiple day ticket after the given birthday, but in that case it will be mentioned in the rules for the ticket.