1. credit is lost after 30day/3month (unless you recharge before).
2. You proably have to change your plan on a (voice or USSD) menu if you want the 30 Day option.
4. I don't know, but probably not, like about all others.
BTW, they will launch their service tomorrow. So they need a basic service working first.
Also, it's the same telecom company of
http://www.breizhmobile.com/
a MNVO in Bretagne, but working everywhere in France (i have a sim card from them).
But with different offer.
I just called them (0800 00 1234 from france, it's a toll free you can probably call this number from outside).
For 3. : they told me yes.
For 4 : they don't know yet, it's a new service so they will call me back tomorrow.
If you have any other question, i will ask them tomorrow.