Hi Rohit,
In WordPress all access is based on Roles and Capabilities. So if you do not see some of the menus or there is a big message saying “Access Denied” it because your user, does not have enough capabilities to either see a page or perform an action.
If I were you, I would spend half to read about Roles and Capabilities in WordPress. Then do next steps with AAM.
1. Make sure that the Administrator role and your admin user have all Backend Menus unchecked (sometimes you can restrict them by mistake or some users experience it when updating from AAM 2.x to 3.x);
2. Each WordPress backend menu has a capability assigned to it. So for example Plugins sections has “activate_plugins” capability assigned to it. If the Administrator role or your admin user does not have this capability, it means you will be not able to access this page. So go to Capabilities tab and search for Activate Plugins capability. If it does not exist, create new capability “activate_plugins” (on the right top cornet of the Capabilities tab there is a button “Create”).
3. In the article above you can find capabilities that are assigned to each backend menu. So perform step 2 for each missing menu.
Regards,
Vasyl