1. Usually bank accepts 3 years financial statements, ITR but it also ask for 5 years in some big cases.
2. For cash purchases limit U/s 40A(3) is applicable ie., Rs.10000 per day per party
3. Section 269 ST is applicable transaction wise or event wise, so if the same is on different dates then there shall not be any problem. However it can always be argued by the officer that the 3 transactions connected & it will be considered as a single transaction.