Does changing the broker, bank account or applying 1st-day 1st-hour change my chance for IPO allotment?

No there is no such thing. As per new SEBI rules, whether you apply for one lot or full lots you stand equal chance to get only one lot in lottery system if retail category is subscribed more than one time. However, if it is subscribed less than one time, then you will get all the lots you have subscribed. So far lottery draw is concerned, it is drawn on a highly sophisticated computer system where you cannot have any manipulations.