Visitor visa for Parents

Hi,

I am from India and have been in UK on Tier1 (G) for last two years. I want my parents to apply for visitor visa. It would be great help if you could take time and answer below questions for me please:

1. Could you please let me know what's the maintenance requirement for them? How much money do they need to show in their account to qualify?

2. How many previous bank statements do they need to satisfy case worker? Can they use Fixed Deposit in this case?

3. What do they need to show to satisfy they will not overstay? My father gets pension, have property (house) in India

4. If I choose to sponsor their trip then how much money do I need to show in my account?

I live in two bed room house. Hopefully, tenancy agreement would suffice to satisfy their accomodation requirement.

5. Does the visa start from issue date or can be requested for a future date?

Many thanks for reading and answering.