Regarding share capital

A company formed on 21 st dec 2016 with 3 directors same as shareholders also with a share capital of 100000 each.But one of the CA said that the above persons have contributed the share capital through his bank account with in 6 months. 1).my query is it compulsory to contribute the capital through bank account with in 6 months? 2).or any resolution is only needed for the same? 3) Is it any alternative? 4). what are consequences if the above is violated?