The Shannon and the Royal Canal. There are many others as Ireland has many rivers and some canals.
A lot
Not all canals were built in Victorian times. Most canals were built between 1750 and 1850 but some were outside this period. There are still around 2000 miles of navigable canals and rivers in the UK.
About 133 miles.
3.
Depends where in Ireland !
About 108 miles or 174 kilometres.
About 147 miles or 237 kilometres.
About 75 miles or 120 kilometres.
About 131 miles, which is about 211 kilometres.
0 miles
About 5,300 miles.