Normally the property is caveat once entering Snp, so if seller doesn't return the earnest deposit, buyer has the right to caveat,. Once caveat, the property cannot be sold.

Every Snp has own risk of default, that's why lawyer always draft clause of forfeiture clause on earnest deposit.

Already mentioned caveat once entering Snp.
In normal situation when Snp collapsed, buyer needs to drop the caveat. Buyer cannot caveat once Snp collapsed, buyer can get sue if continue caveat without reason.

Get lawyer advice, don't just simply doing side deal with seller. Everything follow black and white Snp.
Don't pay cash directly to seller either.

It is called "earnest deposit", to show sincerity in purchasing your property, instead of talk without essence.

Normally, you as seller impose a time frame for it, 2 weeks or 1 months time to sign the SNP (after receive the earnest deposit) to collect 10% downpayment., as you don't want to miss other buyer (if the current buyer doesn't proceed to buy).
Loan approval normally proceed quite fast nowadays if the buyer has the financial capability, or meet the loan requirement.

Please engage lawyer before accept any deposit (including earnest deposit), as it is always need to come with clauses, you don't want some clauses that are in favour, as sometimes SNP can drag too long, which is disadvantage to seller.

Yes, it is normal for seller to show the property title to buyer banker and lawyer to verify the property is indeed yours.
Buyer also scare of fake seller.