Whether the switch WS-C3850-24XU supports the standard 10GBASE-T (IEEE 802.3an) on 24 RJ45 ports?
In DataSheet such standard isn't specified.
Table 12. Management and Standards Support for the Cisco Catalyst 3850 Series
Or it is supported only IEEE 802.3bz and NBASE-T ?
If I am correct, the IEEE 802.3bz and NBASE-T is a capability of the infrastructure wiring, not the switch. The 3850 do have 10GB ports with the correct network uplink modules-
|C3850-NM-4-1G||4 x Gigabit Ethernet network modules|
|C3850-NM-2-10G||4 x Gigabit Ethernet/2 x 10 Gigabit Ethernet network modules|
|C3850-NM-4-10G||4 x Gigabit Ethernet/4 x 10 Gigabit Ethernet network modules|
|C3850-NM-8-10G||8 x Gigabit Ethernet/8 x 10 Gigabit Ethernet network modules|
The multi-gigabit can span 1, 2, 2,5, 5, and 10GB. the 24 1GB ports can ONLY go up to 1GB. the 10GB uplinks can do from 2-10. So if you had a 802.3ACwave2 AP that can do multi-gig, then you use one of the 10GB ports on the network module to accommodate (it will scale down but not up)
I recently installed a stack of WS-C3850-24XUs for a drafting/engineering department that did copper 10G to the desktop for all the engineers on the RJ45 ports. So I would say yes.