Maintenence funds before visa extension + fresh application

[shalinigujral]

I am a student living in UK under international student visa. My visa is expiring on May 15. I have some queries:-

1. Maintanence funds - The rules say I need to have the minimum required funds in my bank account for minimum of 28 days. Should this be for the date the cas is issued or for the date on which I apply on the application form for extension?

2.Suppose I feel my chances for extension are bleak and want to go back to my home country and reapply again what is minimum number of days I can stay in UK before visa expiry. What happens if I have stayed during the minimum day period? will it ruin my chances if I apply for a fresh visa?

3.How long before I can make a fresh visa application from my country after my present visa has expired?

Any replies highly appreciated!