On checking with Allyn Miner’s book on sitar and Sarod,it is noted that Sarod was conceived by one Gulam Ali Khan Bangesh in the first half of 19th century. It is an accepted theory that sitar was invented by Fakir Khusoru (belived to be brother of Sadarang – Niyamat Khan) in the 18th century.Thus it appears that sitar was invented before Sarod.
Q19
Namaste Guruji, would be interesting to know if the Sarod actually evolved after Sitar on noting the differences as highlighted by you