Spain tickets online for Andalusia region

www.seat61.com is the master planning source for rail and has lots to say about buying train tickets for Spain.
Your question is confusing. Do you plan to travel from Madrid to Granada, get off, later continue to Cordoba, and so on? It is my guess that each of these legs will be a single ticket, rather than some sort to hop-on, hop-off itinerary. I'm not familiar with passes for Spain, but will remind you that trains that require seat reservations expect pass-holders to buy those reservations separately. Reservations are included in point-to-point tickets which Trainline.eu will sell you as separate transactions.
It also may not be necessary to return to Madrid. If you are flying in and out of Spain, consider departing from Seville, using a multi-destination search function on an airline or travel agency website.

When are you going? Tickets usually go on sale 62 days in advance, but it's erratic. Sometimes a train will show up several months in advance, sometimes only a couple weeks. I always buy on Renfe's site, but some others here have had success with another options, but I don't know what it is. Often US credit cards don't work on Renfe and you'll need to use Paypal.

I guess we fly from in and out from Seville.

My departure will be from London to Seville and Seville to London back and then return to USA.

So what is the recommendation- should we buy train ticket or get the car rental driving between Cordoba to Granada and Seville and go to a beach one day in Seville. I think having car is easy option instead of train tickets and planning. Just want to know how the driving and roads are there driving from Seville to Cordoba or Granada?

My experience of using both renfe.com and trainline.eu is not the same as yours. Trainline showed me a "single" ticket, not defaulting to roundtrip tickets. Nor does Renfe, if I don't add a return date. There's no multi-city ticket option. Just book each one-way route separately. Almost all Spanish train tickets are sold for specific, reserved dates and times, including these routes.

Driving the roads between cities would be no problem but once inside, cities have a lot of traffic congestion, one-way and not-straight streets, and limited parking.

There is high-speed train service between Sevilla and Cordoba, the ride is less than an hour. To/from Granada, you can take the train or the bus (comfortable tourist-type), depending on the schedules and prices. Sevilla is not on the coast, but you could take the train to Cadiz for a day or stay overnight. The seashore is an easy walk from the train station

thank you!!

Laura, Would you please send your web-link for the trainline.eu that is not the same as I have. Thanks again!!