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
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 is RADUIS server,,,,Am I right ?.

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