@ca

I typed **pAcayati पाचयति in inria and it said (ca. pr. ac. sg. 3)(nI_1), what's "ca"?

Short for "causative". This means that pAcayati पाचयति comes from derivative root **nAyi नायि made by adding /Nic after the root nI नी.

nI नी + /Nic + /laT /tip → **nAyi नायि + /tip → **nAyi नायि + /zap + /tip → **pAcayati पाचयति

**corayati चोरयति shows (pr. (10) ac. sg. 3) (cur). Clearly the affix /Nic has been added after cur चुर् in **corayati चोरयति and after pac पच् in pAcayati पाचयति, so why does inria say "(10)" in one but "ca" in the other?

Because pAcayati पाचयति means "makes someone cook", but **corayati चोरयति does not mean "makes someone steal", it just means "steals". The roots that must get /Nic with no change of meaning were placed in class /curAdi.