1.The SXT are Connected through the Wired POE from the IT NETWORK Equipment Room(DataCenter)..
For Traffic Segeration ..Is it necessary to Sepearte the SXT Network According to.SXT Auditorium -1,Auditorium -2,Auditorium-3 Seperating into different vlan and Network
2.Can we increase the WiFi Strength of SXT
3.All 3 SXT will be Controlled by the RB2011UiAS Centrally for Hostpot Authentication
So: What is your question?
My question is: Why do you name the three APs with different SSIDs? Are positioned in that way they can “see” each other?
No u can not… there is a way but not efficient.
next time to do a good job get NanoStation M2/LocoM2 (Depends on how big is the Auditorium) an a single Access Point
About the HotSpot, u can configure 3 diffirent hotspot services on each port on the RB2011UiAS to complete your task!
No it is not necessary to separate them.
This depends on your local regulations. You cant increase the power of the mobile devices so it might not increase your coverage to increase power at the ap. The right placement of APs is the key. Use a signal detection tool with your smartphone to see if you get signal everywhere.
Ok.
Or aruba or meraki or …
You want us to buy another product ? Guess what: Your gear has the same Atheros-HW inside but a very limited SW.
Nevertheless designing a hotspot for an auditorium might be a difficult thing depending on what is your auditorium. Occasional Users are no problem. But if there are 1000 IT-Persons in the room you might have to design your network very carefully and use all free spectrum with good (beamforming) antenna systems.
This is where Tools like Ekehau Site Survey comes into the game. And this is where I would leave the UBNT/MT-World as none of them has special designed antenna systems to get the maximum out of the spectrum.
Good Point, but do you really believe that those who own the auditorium will give it to “solutionamar” if they expect 1000 of IT oriented creatures 
We all know that if we have the money to buy the good stuff all is OK
the idea to share an “ideas” like solutionamar’s is to find a low-cost, but efficient solution for him in the particular moment!!!
Use a signal detection tool with your smartphone to see if you get signal everywhere.
Better yet, use the client registration list to see your smartphone’s signal strength from the radios. The access points can typically provide a stronger signal as they typically have higher power transmitters and not necessarily higher sensitivity receivers, and also different antenna gain/patterns. It’s only going to trick the mobile devices with their tiny antennas if they see a strong signal from the access point, but can only provide a weak signal back.