When router learn multiple routes to specific network via multiple routing processes ( routing protocols, such as RIP, RIPv2, IGRP, EIGRP, and OSPF)?

The router will choose the most specific and closest  route regardless of the administrative distance of the routing protocol, for instance: if the RIP route has /24 net mask and OSPF has /16 net mask, then the router will choose the RIP route over the OSPF.

If all the learned routes for the specified network are the same, meaning that RIP and OSPF routes have /24 mask, then the router will choose based on the administrative distance, in this example where only OSPF & RIP, OSPF will win.

If EIGRP is added to the protocols, then EIGRP will win, again, that's only in case of no closest route

The route with the lowest administrative distance is selected. In this case, EIGRP wins because its AD is90