Whether to create 32 bit or 64 bit DSN assuming your installing ESX on x64 Windows Operation System?
==>DNS should be always 32 bit irrespective of 32 bit or 64 bit OS for vCenter. when you create DNS on 64 bit OS, 64 bit DSN is created by default. in order to create 32 bit DSN invoke utility from [WindowDir]\Syswow64\odbcad32.exe
What is the character limit for naming server on which you install
it is 15 character (SPNQ15U10831)
What privileges are needed for installing Database –on MS SQL
User must have DB Owner rights on VIrtual Machine DB and MSDS while installing and upgrading Virtual machines. once this activity is finished these high privileges can be revoked and assigned normal rights e.g. db_datawriter and db_datareader permissions.
Why you cannot join Linked mode group during installation ?
This generally happens when you choose not to re-initialize database while installing DB. But you can join linked mode once VC installation is complete.