I would like to take the RER B from CDG to St Michel N/D, and transfer to the RER C to to get to my hotel in SQY. I'll have a bike in a large cardboard box. Do all trains have a bike area or just the express lines? Do I need to get a second ticket at N/D or can I buy a ticket a CDG that gets me to SQY? Are there any other problems I might encounter? Arriving 8/14, leaving 8/24.
On the RER B and RER C, the two lines you'll take when going from CDG to St-Quentin-en-Yvelines (my guess what SQY means), there will be space on the trains for luggage and bikes.
You can buy a single ticket to get you the entire distance of CDG to Paris - to St. Quentin. Buy your RER ticket from the ticket staff and they'll customize a ticket for this trip. It'd be easier than trying to purchase such a ticket from the ticket vending machines.