Q1.what's the difference between radgroupcheck and radgroupreply?

radgroupcheck is similar to radcheck. These tables are “checked” to authorize/authenticate a user.

radgroupreply is similar to radreply. These tables have the attributes that are sent back to the NAS in the reply packet.

use radusergroup to map users to groups.

Q2. if i want to add a group which users in that group can have the limitation: it will expirate in 2 days? how to set the attribute...

If you want to send back an attribute for all users in a group, add an entry to radgroupreply.

Tim