The purchase value of the old shares would remain the same as your purchase price and the value of the bonus share will be treated as zero. The date of the receipt of the bonus shares would be treated as purchase date for bonus shares and when you sell these bonus shares, the short term or long term capital gain will be calculated depending upon the time duration of sale of these bonus shares.
Split Shares would retain the original purchase date but the purchase cost would proportionately adjusted based on the split ratio of particular stock.
In case of Demerger, the new shares received of any new companies would be treated as of the same date as of the parent company. If you want, you can manually change the effective purchase date of a new company. You can also set different dates for different quantities of the same new company by entering details in each new row.
In case of Merger, the original purchase date would be retained for the new company.