So... there are two sets of dates that are relevant for your question. One set to do with the purchase / sale of the equity and the second to do with the dividend.
When you buy a security you have a "trade date" (TD) - the day the trade is executed which could be different from the day you call the broker if you call late in the day and the "settlement date" (SD) - the day you pay for and receive the shares. You talk about buying on a T10 basis - I'm surprised at that. Most western markets are T+2 or T+3. Some have even moved to T+1. But the settlement cycle is pretty much irrelevant.
On dividends, there are three dates; Ex Dividend Date, Record Date and Pay Date (these days, the first two are often the same - they used not be). In essence, any one who holds the equity before the Ex Date is entitled to the dividend. Anyone who buys on or after the ex date is not (there can be a bit of messing around on the institutional trading side where some trades on Ex Date are "cum dividend" - but you can ignore that tbh).
The secret is that irrespective of registration of ownership (or settlement cycle), you have full economic participation in an equity from TD. And if TD is before Ex Date you receive the dividend. Likewise, if you sell the security on or after Ex Date, you will still receive the dividend on Pay Date (even though it may not be in your name any longer)