Can we buy 2 passes each such as 21 day + 7 day or 2 of 14 day to cover whole our stay?
Yes, there is no limit on the number of JR Passes you can buy. It's worth bearing in mind the per day costs of the JR Pass reduce as you purchase larger passes. For example:
- 7 day = ¥4043/day
- 14 day = ¥3221/day
- 21 day = ¥2747/day
As you mention you have 2 choices: 2x14 day or 1x21day + 1x7 day. Here is the per day cost breakdown of these choices:
- 2 x 14 day = ¥3221/day
- 1 x 21 day + 1 x 7 day = ¥3071/day
Based on this I recommend you purchase a 21 day pass and a 7 day pass as this combination will be the cheapest per day over your trip.
Hope this helps!