Dell Optiplex 790 Network Drivers Download Windows 7 64-bit

I have just joined dell forum. Recently I have moved into new organised wherein I have been given old OptiPlex 380 ( 2011 model) for couple of months till I get laptop. I happened to upgrade this desktop to Windows 10. I have all the drivers setup correctly and upgrade is fine except for below two issue :

1. My LAN is not detected post upgrade

2. I Struggle with supporting Video drivers for Intel Graphics

For Issue 1 : LAN is not detected post upgrade

I have run the full diagnostic test for Dell OptiPlex 380 on Dell site, successfully passed test for Broadcom Network Ethernet card.

Observation : When I go to Network & Sharing Centre, go to Change Adapter Settings, even though I have LAN cable connected to my desktop, but it shows "Not Connected". I have this same LAN cable working before upgrade, because that is how I was connected to organisation network, and did my upgrade of Windows from Win 7 to Win 10.

So this is all that I have done so far for this issue :

I have an issue on Dell optiplex 990 windows 7 64-bit in network speed, actually in the network switch port configured as auto-duplex and auto-speed and normally all clients negotiate based on the link speed configured on the client. Other clients perfect working with 1G link speed same network switch configuration of all other ports. Note, the IP address of the Dell is static and joined to domain.