Login Script Based On Email, IP And Sql Server Backend

My questions concerns building a login system based on checking for the
existence of the user's email address only....

1. Is it ok for me to use IP address to allow user to bypass all login and
registration systems if IP is present in database? I wish to save the user
time....if the IP is not present I will present the LOGIN email screen....

2. I am consideirng using Session variable on each page I wanted I
protected...I think I know how to do this but I am not sure on whether I
should be using the global.asa to handle loggin in or logging out or whether
I should so all the code on the secure page itself.

3. I wish to use a sql server backend to house my tables: tblProspect,
tblProspectPageSelections......is it okay to use the following branching
code to switch between my test and production server with regards the
physical database path as I have multiple sites on our remote server which
need to feed off the same database....I am thinking about something like
this:

If InStr(Request.ServerVariables("SERVER_NAME"), "publicserver.com") > 0
Then
' Set Public Server Paths
Else
' Set Private Server Paths
End If

Can this work?