Train tickets/classes... confused?

The above answers are correct, but there is slightly more to it. If the railway cancel your train, or you have a connecting train and the 1st is late, then you can travel on a later train. If YOU miss the train, your ticket is invalid and wasted.

Nope the conditions of carrage are quite strict with advance purchase tickets which are named fro a certain service at a certain time. The only time they are transferable is at times of severe disruption or disruption on journey by another operator, and even then you have to buy a new Standard Class ticket and claim back from the TOC which caused the problem. At that time of day the only other option is a Standard full price ticket, unless you can wait until the Saver Option is permitted, check with your local station for times.

The ticket that you have brought will only be valid on that specific train. If however, the train gets cancelled/delayed and you have to get on the next train then your ticket will be valid as it is no fault of your own. But if you miss the train from being late etc then you will be charged another fare.

No you can't, if you try and use it on any other train you will be treated as having no ticket and have to pay the full fare for that journey.

No, your ticket isn't valid on any other train. They'll charge you full walk up fare if they catch you on a later train with the wrong ticket. Don't be late!