About two days
You can't travel directly from Heathrow to Bristol. The best way is probably to take a bus to Reading and get a train from there or travel into Central London and get a train there.
about 20 h
About 4 hours
About 2.5 hours
About 35 minutes.
There are no trains from Minnesota to London, England. Train travel is not possible across the Atlantic ocean.
You can't travel directly from Amsterdam to London by ferry because London doesn't have a ferry port. You would have to travel from Amsterdam to Hook of Holland by train (or drive), catch a ferry to Harwich and then take a train (or drive) to London.
The Eurostar train takes around 2 hours and 15 minutes to travel from London to Paris.
I suppose that 50 hours is sufficient.
About 1 hour 30 minutes by train.
Malta is an island in the Mediterranean Sea so you can't travel there by train from anywhere.
About 4 hours 30 minutes.