Hi Andrei,

> And how to draw rectangle from center on the end of curve to make it perpendicular?

You can either set the CPlane using View > Cplane and snap on to the end of the line, or also if you drag out 2 crossing construction lines from the end that will then form a snap plane aligned to those construction lines for just that pick, see here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=5407.9

- Michael