Hi @JMAFO ,
Based on the needs that you mentioned, I think PowerApps could achieve your needs.
For your first question, on your side, you could consider generate an app based on your SP list, then an app with three screens would be generated. After that, you could use this generated app to add, delete, modify records in your SP list.
More details about generating an app based on a SP list, please check the following article or video:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/app-from-sharepoint
https://www.youtube.com/watch?v=qwUt7MagAt4
For your second question, within the first screen of above generated app, it contains a Gallery control, which used to list records of your SP list. If you want to retrieve the list items in 6 months, you could consider take a try to filter your Gallery items using Filter function.
I have made a test on my side, please take a try with the following workaround:
Set the Items property of the Gallery to following formula:
SortByColumns(
Filter(
'20190108_MainList',
StartsWith(Title, TextSearchBox1.Text),
Created >= DateAdd(Today(), -6, Months) /* <-- Add this formula here */
),
"Title",
If(SortDescending1, Descending, Ascending)
)
Best regards,