@dtrader Ji
Pre-IPO placement is exchange or allotment of equity between promoter and investors before opening of IPO for general. It maybe done at lesser price or IPO price. It's decision of the company.
Usually companies keep a small portion of total IPO for Pre-IPO placement to test demand of the IPO in market and these are allotted to institution or big HNI. This is optional for the company. They have lock-in of share for certain period.
Anchor allotment is part of IPO process where it is mandatory for the company to reserve a portion of IPO i.e 60% of 50%/75%(QIB portion) for anchor investors who are institution whether FII or DII. It is always allotted at IPO price and one day before opening of the IPO.
It's prerogative of the company whom to give allotment in the anchor book. The anchor investors too have lock-in of share for 30-90 days.