Why suddenly Alexander is Murauga Avatar - I dont know.
For Both Muruga and Ganesa, we have one more place.
1. The thirupparamkundram Cave.
It is sung by sambandar - 6th Century
2, It has both Muruga with deivanai ( hence the statement of Murugan was alone till 9th century is ruled out) then a Ganesa in the same cave who is pre sambandar.
Can any one give details on thirupparamkundram cave. That will help on finding the timings.