Onshore Compensation for TCS Australia (Perth Location)

Recently got a opportunity to work onsite in Perth Location. C2 Grade.

I am confused what will be my onsite pay. I read somewhere they convert India Monthly Pay to AUD and daily allowance 80-100 AUD to calculate Gross Pay. Then, tax deduction will happen on top of Gross Salary. Is it true ?? Or we will be provided with C2 grade equivalent salary of TCS Australia branch ??

Whether I will be getting my compensation letter before initiating VISA request ?? I think its essential to know exact compensation before making this big decision to move to onsite.

Help me out with this.