stay of demand

no, not necessary. first you apply for stay of demand before assessing officer. after considering your application, he will either grant you stay, setting forth some conditions such as he may grant you installments for payment of demand or he may reject the stay. he will convey this by letter in writing. then only according to letter, you have to pay the demand. no need to deposit 20%, before filing stay application
20% of demand has to be paid, if you are filing appeal before CIT(A). But nothing stop you to file appeal before paying 20% of demand. appeal has to be filed within 30 days from the date of service of order in question

yes it's necessary... first you need to file appeal petition before cit(A) and after that you need to pay minimum of 20% of tax demand before filing stay petition.

Thanks a lot. Also advise that is it binding on CIT(A) to grant stay after deposit of 20% demand.

no it's not binding on either AO or CIT or cit(A) to grant stay

Thanks a lot. Also advise that is it binding on CIT(A) to grant stay after deposit of 20% demand.