Microsoft
MicrosoftRasnaSaini Dividend dates and Ex-dividend dates are not something currently licensed to us by our data provider. It is one of the top asks from customers like you though, so I understand how it would make sense as a factor for historical analysis. I encourage you to vote for the item here: https://excel.uservoice.com/forums/304921-excel-for-windows-desktop-application/suggestions/35122639-add-dividend-data-to-stock-data-type on UserVoice. I can't make any promises about when/if we can get the data, but it is on my radar.
For Stock Splits, when the stock split data flows through to our system, there is a latency period, on the next recalculation of the StockHistory function (this could be on file open, function edit, or because the function is volatile with the Today() argument etc), the results will update to show the historical prices calculated to reflect the split. This will feel very similar to what you may see on websites like MSN, Google, and Bing when showing historical prices https://www.msn.com/en-us/money/stockdetails/nas-msft/fi-a1xzim
There wouldn't be a way to "freeze" the numbers from the result unless you performed a copy and paste as values for the data before the Split. Does that make sense? What do you think?