Yes you can. On 2 travel days you may travel in your country of residence.
Only note the mandatory reservations on French fast/high-speed trains and Eurostar. The latter could sell out a few days in advance.
Switzerland - Paris TGVs cost 29€ (1st class 39€) but you can cross the border on a regional train (to Bellegarde, Mulhouse or Strasbourg for example) and then take a TGV within the country : 10€ limited domestic fare, then 20€.
Thanks thats really helpful. Its possible i could get home and have an entire spare day left. Can i use that day in any way i choose?
Thanks thats really helpful. Its possible i could get home and have an entire spare day left. Can i use that day in any way i choose?
Yes, but the limit of 2 travel days in your country of residence still applies. If you've used those, then you can only use the remaining day abroad.