If dc motor is run in reverse as generator.shal it generate ac or dc current
It would generate AC, I believe. In order for it to generate DC, it would additionally require a rectifier, filter and regulator circuits on the output, which would change the AC output into DC.
It will generate AC because AC will not require a rectifier or regulator circuits in the output. DC would need a filter besides the others for magnetic power to increase and be efficient.
A DC motor run by another motor will definitely produce DC current.Essentially because this is how all power is created it is then changed to alternating current.