In general the following sites can help you. Country specific sites follow
I’m starting off with trains as getting home from a leisure cycle is good with trains.
Seat61 – will tell you bike on train rules for any country in Europe
Loco2 – this site allows you to buy tickets on regional trains and compare various prices. Does online tickets for quite a few countries
Rome2rio – will gove different options for getting from A to B.
mapmyride has good elevation data
Bicyle Routes and Tours has 723 long distance routes in Europe with lots of useful information about sights and attractions
Pisteciclabili.com – lots of cycle routes with elevation ( in Italian)