3. Can we upgrade McAfee agent with current ePO 4.6.6 setup form 4.5 to 4.8?
6. Can we access epo Console using Web Browser only or is it required to install anything on client machine to access my ePO console?
No need to install anything on client unless you are using DLP, then you'll need to install the DLP management tools. But standard web browser is all you need to access the ePO console.
As per the other questions:
1. what next ePO version can be upgraded directly form ePO 4.6.6 ? and will there be any OS/DB dependency ?
You can upgrade to ePO 5.1 (ePO 5.0 will be OEL on december) but it requires being installed on Windows 2008 x64, Windows 2008 R2 or Windows 2012 (std or R2) and also an SQL 2008 database
2. Will there be any challenges for current Policies and configuration?
I don't think you'll have any problem with them except for VirusScan 8.7 that is not supported under ePO 5.1 (you should first upgrade to VSE 8.8)
4. Best practice to upgrade Mcafee agent for Win 2k3,2k8,2012 and linux machines/vms?
There's no specific requirement, just set a new task to upgrade McAfee Agent (both on Windows or Linux)
5. can we upgrade existing ePO 4.6.6 to latest build/ patch without purchasing any new licence ?
Having a valid Grant Number allows you to download any ePO version and any patch
7. most of the times we are unable to push agent upgrade form epo console to inventory..how can we proceed further to overcome this issue?
This is usually caused by a firewall or by a DNS resolution issue. Check this: https://kc.mcafee.com/corporate/index?page=content&id=KB56386
8. what should be the best config of ePO if i have multi site inventory?
If you have different sites with more than 20 computers it would be best to create superagents or distributed repositories on each site so computers can download packages locally instead of connecting to your ePO server
Can we go for direct upgrade from ePO 4.6.6(176) to latest ePO version? any special instruction /doc/tool to be followed to get this upgrade directly ?
and if we have OS Depdnecy ..like for latest version i would need Win 2k8 R2/64 bit OS..can we get all inventory/polices/db form old epo to new ePO Server with new databse ?
I have 4-5 remote sites with tolat; 12k clients..so what would the best confige for ePo Setup ?
is it required to have seperate Mgmt and Policy Server ?
any helping doc for creating superagents or distributed repositories on each site?
Can we use inventory fetched by some other inventory tool to get this imported into ePO ? any specifc way to import data for diff environmnet with diff tag inventory ?