Is separate account mandatory to allot shares for capital

Hello experts, 

We have registered a Pvt Ltd and also got MCA approval for further increase of authorised share capital to from 1Lakhs to 5Lakhs by increasing no. of shares to 50000 of Rs 10 each.

To manage the operating expenses, director has been infusing money into the companies bank account to the tune of 2-3 lakhs by end of this month. In return, he is expecting to buy back equal value of shares (from 50,000 above).

I have few questions.

1. Can we allott the shares equal to already transferred money to the director. What's the procedure.
2. Is a separate account mandatory as per new company law for even smaller amounts of investment from directors.
3. Is it only necessary for external investors (not current directors)?

Thanks in Advance. 

JV​