How to create the 3 WLAN networks in sophos UTM?

Please show pictures of the Edits of the relevant configurations.  When you say "after creating the Hotspot, WLAN is not reachable,"  What are you seeing/doing?

Cheers - Bob

now the WLAN is working after renaming the Hotspot WLAN.

but now the main issue is,  I have the WLAN on one physical eth interface with IP address 10.x.x.x/24. I want to use this IP network for all 3 WLAN networks (Guest. employee, Internal).

How can I use one whole network for 3 different named WLAN networks?

should I split the network or are there any possible solutions for this issue!

It's difficult to understand what you want without seeing a diagram with IPs and subnets.  A picture of a hand-drawn diagram would be good.  What WiFi Access point(s) are you using?

Cheers - Bob

Here, the WLAN 10.x.x.x/24 network. 

from this network i need to create 3 different WLAN networks for (guest without password and just accepting the terms, employee with password, internal with Certificate).

 when i configured the guest network via hotspot from Wireless protection with accepting terms and conditions it was working and employee wlan with password also working.

but how to include the certificate for the internal WLAN with SSO.

When you define a Hotspot on an Interface, all devices connecting to the Interface will be forced to use the Hotspot defined on the Interface.  If you want three different connection types, you must define three different Interfaces - three different Wireless Networks.

There's no way to use SSO to login to a UTM-managed wireless network as WPA2 Enterprise uses RADIUS instead of an Active Directory login.  I can't think of where a certificate is considered in UTM Wireless Protection.

Cheers - Bob