JR Kanto Area Pass

I will be traveling to Karuizawa and Kawaguchiko with the JR Kanto Area pass.

Questions are:
1) Does the JR Kanto Area Pass cover both the fares and supplement fees for the limited express trains (N'EX/ limited express Kaiji) and shinkansen (Asama)? Do we need to top up the supplement fees?

2) From what I read, supplement fee has to be paid when riding the observation car of limited express trains by Fujikyu Railway. What is this observation car? How much is the supplement fee? Is supplement fee still needed for a normal train on the fujikyu railway?

3) I understand the pass cannot be bought online? But I can make seat reservation online?

Thanks in advance!
Elza

1)
No need supplement fees for all but need seat reservation ticket before
Only N'EX are no cars train. (all Kaiji/Asama have both)
If want reserved "Green" car seat needs green car fee all.
Ordinary car means reserved and un-reserved cars only
Green is not. http://urx2.nu/gNkO

2)
http://e.fujikyu-railway.jp/train/
http://www.fujikyu-railway.jp/train/fujisan_express.php
No online sales.

3)
Pass no sales online but only seat booking possible.
http://www.jreast.co.jp/e/kantoareapass/index.html
http://urx2.nu/gNmn