REServations are needed for IC trenes (comboios) and can be done at any station(where there is staff-that is about any stop for IC-trenes), cost is 5€, though someone has told lately it was only 4 if you do it advance. It can include 1 connection. You can also ask conductor @ platform if there are spare seats and then s/he will pass by and sell you-at a slightly higher price. This is mostly meant for minor stops or when counter is closed.

The GATES (very much like your RENFE has for cercanias) are only around Lisboa and only for local train, where there is an integrated fare-system also for bus/metro etc-also like Madrid has. Just like RENFE you have to contact staff-probably those sitting behind the glass counters selling tickets-and they can open remote. IF there is no staff-then apparently you have bad luck and cannot enter with or use pass. But these are short trips with very low fares.

NOte that CP also has its own POrtugal Railpass, which offers a little more and for some nr of days even cheaper as IR/1 country. Google it. There are also local/regional passes for Algarve and the north-in the past also for junior+ some youthHostel nights included. For around Lisboa there are also local passes for not just tren, also metro/bus and these come on the chipcard (Via Viagem) so no prob to enter gates.

Buenes viajes and please be kind tell us afterwards if things have changed or are otherwise-then we can inform better new travellers.

You can book Spanish trains at any Spanish long distance station with a ticket office. You can also call RENFE for reservations in Spain but then you have to pick them up at a Spanish station within 72 hours and you have to call more than 24 hours before departure. See this page for details (click on "En la estación de tren”).