If you use fonts in Adobe applications (InDesign, PhotoShop, Illustrator), and the fonts are missing or appear corrupted, search your computer for all copies of the file AdobeFnt.lst (for example, Adobefnt01.lst ... Adobefnt12.lst) and delete them. The easiest method is to search your hard disk for all .lst files.
TPTQ Arabic fonts are Unicode compliant, so you need to enter your text correctly encoded. An easy way to find out if you have correctly encoded text is to copy-paste a sample of the text into Internet browser, for example into Google search.
Some old text documents working with Arabic or Indic languages use 8-bit encoding, which required to use proprietary fonts. Such fonts can only use 256 glyphs, which is not sufficient for correct rendering of Devanagari (or other 10 Indic writing scripts).
Just go to Glyphs, on the font presentation page.
OpenType is a computer font format that was built on its predecessor TrueType, intended to supersede both the TrueType and the PostScript Type 1 font formats.