Short selling of Stocks

I have short sell 42000 shares of vakrange but it hit the upper circuit. Can I buy back the shares on next day when the market opens…

No, that’s not possible. You need to close the position before the end of that trading day otherwise your broker will close your position at whatever price it gets and will also charge you penalty.
But if you were doing it in F&O you would have the option to carry forward your position.

No, your trade will be considered short delivered and the exchange will conduct an auction to buy the shares you did not deliver for the buyer on the other side of your trade. Learn more - What is short delivery and what are its consequences?

Today I got the auction contract where the auction amount is showing say 20000 but in zerodha the amount which is blocked is 35000.
Will I get back those 15000 ??

@Rksh Auctions are not mandatory hope it helps you to understand: Youtube - A new way of manipulation and Scams! - #36 by tradewealth