On record date the share should be there in the account So selling on 29th or on a later date looks ok. If one want to tender it then he can buy it again one day before the tender closing date.
@Vimal The shareholders on the record date become eligible to tender shares. One may sell on the next day and buy again so that they again have the same quantity in demat a day before the end of the tender offer. That way they can tender the shares and avail buyback.