Kindly look at this link below (i know it is oracle) , you can see the Oracle server has got another name which is RADUIS client as well
Figure 5-1

Does the similar concept apply to VPN and RADUIS and SecureID (Token) ?(i.e. VPN is Raduis client )

2- In the diagram below :

Which one is RADUIS server and Which one is RSA ACE/Server ? My guess is the middle one is RSA ACE/Server.

My confusion is in the first link RADUIS server sends requests to a proper server,,,ok,,,,, while in the second line (auckland diagram) the case is vice versa (i.e. RSA ACE/Server sends requests to the RADUIS),,,Any insight ?

3- if I have got cisco RADUIS server , do I need to use RSA ACE/Server as well , because RADUIS does support two-way factors Authentication
RADIUS is a two-factor authentication method based on something you know