the 4th vs Itachi would end with Itachi's death.
Jiyaira is a match for Itachi - the 4th would throw him aside like a ragdoll

Itachi wouldnt attack while the 3rd was in power why would he stand a chance against the 4th

if i could reverse time i'd put Orochimaru, 1st Hokage and 2nd Hokage up against Itachi and watch him get slaughtered