So I just read Spain is extending their free train travel promotion until the end of 2023 ... these are for Renfe commuter trains and Medium Distance (less than 300 km or 186 miles), so doesn't include any high speed AVE or (I think) AVANT trains ... so for my purposes, it looks like the only tickets I need to buy are between Madrid and Cordoba since that route is over the limit (Cordoba-Granada, Granada-Sevilla and Sevilla-Cordoba all fall under the 300 km limit) ... there is a small $20 deposit that is refunded if you take 16 or more trips but I'll gladly forfeit that for my 3 trips.
Question? ... does anyone have with first-hand experience on how this works? ... do you need reservations for the MD trains (or can you even get them)? ... do you just show up, get on a train and sit wherever? ... might be worth the extra travel time to save some cash.