Can I downgrade from version 3.2 to 2.9 ?
No.
RB333 is only supported in ROS 3 and higher
What a pity…
V3.x really s*** 
(
I have only problems after upgrading to v 3.x
PS: sorry Normis for my impolite word 
what kind of problems?
Speed of WINBOX decreased after upgrading to v 3.x on RB532.
=> Accessing RB532 with v 3.x spare 10times more time then before.
I am not sure, but I think that speed of my RB decreased too.
And other problems.
For example look here:
http://forum.mikrotik.com/t/v3-2-bug/18851/9
or here
http://forum.mikrotik.com/t/routeros-v3-1-and-v2-9-50-connecting-problems/18763/1
or here
http://forum.mikrotik.com/t/ros-2-9-50-3-x-clients-possibly-incompatible/18420/19