Hi,

used font:
http://fonts.qurancomplex.gov.sa/wp-content/uploads/2012/06/UthmanTN1-Ver10.zip

Minexample:

\definefont[uthm][file:UthmanTN1Ver10*arabic at 20pt]

\starttext
\uthm
\setupalign[r2l]
???????
\stoptext

You see, that the letters are not connected, it should be look like the 
attached image with this ligature.



In the image you see the same font and the same above unicode-text, but 
rendered with CorelDraw instead. So it may or may not be a font-issue, 
but solvable in ConText?

Thanks.
Huseyin