Reservations in advance and change afterwards

Often yes, although for some trains it is possible to change the reservation.

It also depends on where you book your reservation.

For those that cost like 5-6€-forget it, that will be lost.

For higher priced-check on the mail you get with it what do in such a case.

BTW: you must be the very first one from Gibraltar to post here-welcome! Now I wonder what homecountry is-simply also ESpana (oh my dear. what a disgrace) or that they allow you also unlimited travel on RENFE. Same may apply to those from like Andorra, MOnaco etc.

Here is a question, since Gibraltar has no railway but is in Europe  do you get an interrail  or Eurail pass?

Obviously both will work as universal passes in all 33 countries with no home country limits. 

Gibraltar is definitely noti n Spain and nearest Renfe is Algeciras.

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As Gibraltar is a part of Europe you need an Interrail pass. 

Hi @Troy Charvetto Gomez 

Like @AnnaB already mentioned, it depends on the reservation you have. Most of them are not or partially refundable. I would recommend making reservation when you are entirely sure you are travelling on that route.

Have a lovely day!

This is correct. @Yorkie @mcadv. 

I invite you to read the point 2.1 of the conditions of the Pass, which you can find here. 

2.1 Interrail Pass eligible customers
Interrail Passes are available to all persons in possession of a valid passport/identity card or a residence permit of one of the countries of the European Union and the countries listed hereafter, or persons officially residing in one of the countries of the European Union and the countries listed hereafter: Albania, Andorra, Belarus, BosniaHerzegovina, Faroe Islands, Gibraltar, Iceland, Kosovo, Liechtenstein, Moldova, Monaco, Montenegro, North Macedonia, Norway, Russian Federation, San Marino, Serbia, Switzerland, Turkey, Ukraine, United Kingdom and Vatican City.