About 7 hours
You can't travel from Edinburgh to Belfast by train because Belfast is in Ireland which is an island. The easiest way is to fly.
About 4 hours.
About 2 hours 30 minutes.
About 3 hours 30 minutes.
About four hours and you will have to change trains at York.
About 4 hours 30 minutes.
that makes NO sense.
There are no direct trains between Holyhead and Edinburgh - you will have to change trains at least once. The journey time will be about 6 hours dependent on which train you catch.
You can't take a train directly from the Shetland Islands to London. You can't even fly directly between Shetland and London. You could travel by boat from Shetland to Aberdeen and then take a train or fly from there to London or you could fly from Shetland to Edinburgh and either fly or take a train from Edinburgh to London.
Anything from 3½ to 4½ hours depending on number of changes.
Typically between 2.50hrs and 3.25hrs and with one change at Newcastle.