We have two ISP's named as A and B, are connected with RV325 Router. Is it possible to route A ISP to specific private IP without NATing
Without NAT your endpoint requires a public IP address - generally, you can only connect public-public and private-private without NAT.
(It is possible to mix public/private in certain scenarios like a public-IP DMZ that is connected to your LAN router directly.)
If you want to route a specific destination through a defined WAN interface you can just set up a route pointing that way, e.g.
184.108.40.206/32 -> ISP A. Depending on the device at hand, more specific routes (longer prefix) are usually preferred before less specific routes (short prefix). If not you can use route metrics to set the preference.
You will need to the router to have policy based routing and or source based routing which will let you specify when to route the traffic acrross ISP A , what are you trying to accomplish? Do you want traffic that matches your ISP A public IP to go directly to an specific host in your LAN? , if that is the case you could try using portforwarding but NAT is always going to be there as long as you use Private and Public IPv4 routing.