Mumbai, Sept. 27 -- Private equity (PE) firms that hoped to exit their investments through initial share sales are forced to defer their plans as volatility continues to rock India's stock markets. Between 1 January and 14 September this year, 29 companies chose to let regulatory approvals for their initial public offerings (IPO) lapse, data from primary markets tracker Prime Database showed. There are still 22 firms holding valid approvals, but they too will lapse by end of December if they do not list by then. A company has to get listed within a year of getting the go-ahead from the Securities and Exchange Board of India (Sebi), or refile the draft offer document and seek fresh approval. "PE-backed companies have already begun exploring ...