I clean installed windows but no change.

Here is more info into the exact details:

NVIDIA GeForce GT 635

Windows has stopped this device because it has reported problems. (Code 43)

Device instance path:

PCI\VEN_10DE&DEV_1280&SUBSYS_103210DE&REV_A1\4&519621C&0&0008

Hardware Ids:

PCI\VEN_10DE&DEV_1280&SUBSYS_103210DE&REV_A1
PCI\VEN_10DE&DEV_1280&SUBSYS_103210DE
PCI\VEN_10DE&DEV_1280&CC_030000
PCI\VEN_10DE&DEV_1280&CC_0300

Compatible Ids:

PCI\VEN_10DE&DEV_1280&REV_A1
PCI\VEN_10DE&DEV_1280
PCI\VEN_10DE&CC_030000
PCI\VEN_10DE&CC_0300
PCI\VEN_10DE
PCI\CC_030000&DT_1
PCI\CC_030000
PCI\CC_0300&DT_1
PCI\CC_0300

Status:

01802400
DN_HAS_PROBLEM
DN_DISABLEABLE
DN_NT_ENUMERATOR
DN_NT_DRIVER

Problem code:

0000002B

Did you get the windows 10 drivers from Dell? XPS 8700 is approved for windows 10 and Dell has provided win 10 drivers at Dell Support, Downloads and Drivers. Allow it to scan the computer and install the necessary drivers. Worked very well for my 8700. 

They did not work for me. I tried to uninstal and reinstall the drivers but still  nothing.

i had the same problems as you and if you restart the computer my second screen works and sleep comes back. 

I found out it was a problem with my video card as it stopped working completely. I upgraded it and boom everything is working perfectly. Sleep mode is back and no more code 43.

which card did you  get

I would recommend EVGA 04G-P4-2747-RX  GT740

http://www.newegg.com/Product/Product.aspx?Item=N82E16814487208

I got the GIGABYTE GEFORCE GTX 750Ti Windforce OC edition it has been working great so far.