Cancelling Estate Agent Authority

My friend and I bought a house and each person own 50% house. A week ago, we signed a Estate Agent Authority for auctioning this house. However, my friend now change his mind. He does not want to sell the house any more thought I still want to sell the house. He told me he will call agent to cancel the action without my agreement.

Can someone tell me what will happen in this circumstance?

1) can he cancel the agent authority within the exclusive authorised period without my agreement? if he can cancel? will we have any6 liability to the estate agent?

2) if I definitely want to sell the house to get back my shares of the house ownership, will he be forced to accept house auction? I ask this question because he told me that he wants to buy my shares at the estimated price but do not want to auction the house.

3) In case we go to court to solve the conflicts, will the court put the house in auction?

Thank for your help.
Whether he can or can't is kind of immaterial. You can't sell it (i.e. contract for sale) without his signature.

You'll both have to agree to sell. In the absence of that you're only choice is to hold. I'm not a lawyer, but that's how I see it unfolding.
Houses aren't always guaranteed to sell at auction, and the legal and emotional costs of fighting a friend in court are likely to be far more than the extra couple of grand that you might (or might not) have made at auction.

If you really want to cash out of the house then take what he's offering (Assuming the estimate has been carried out by a professional valuer). It seems like a fair deal and there is no way that you will be able to force him sell without his consent.
I think you'll find that as you have signed an authority for an estate agent to sell your house, you will have to pay his/her commision even if you only sell your half to your friend. IE: if your contract period with the estate agent is for 3 months, and you sell to your friend within that 3 months, then the agent is legally allowed to take the commision even though he/she didnt do anything to get the sale.

I could be wrong, but check it out first.