Backtesting limitation of dates is put in place to avoid false signals and make it much easier for you get get the right results, to validate for a specific day, just run the backtest with the last day as the day you want to check, and then in transactions log look at the last few trades. We had to put this restrications in place after many continous queries and requests from a large number of clients.
This can be done, in a single click, just click on the convert to strategy button, and automatically your scanner becomes a strategy(if you select the stocks before clicking on the button, then become part of strategy too), and you fill other details(like tp/sl) and backtest. This was recently released as Create Plus, read more about it here https://medium.com/streak-ai-tech/update-streak-introduces-create-plus-and-more-9dbd1e1e4417
Also these create plus backtest are 10X faster just like scanners, you click and you have the results.
Hope this helps