What are the main requirements and limitations of the Pine Screener?

1. The Pine Screener is only available to users with a Premium subscription and above.

2. Only one indicator can be used in one screen.

3. The indicator must output at least one plot or alert condition from the plot() or alertcondition() functions to be used as the screening filters.

4. Only the plots of the selected indicator can be used as columns.

5. The Indicator-on-Indicator feature is not supported.

6. Custom timeframes are not supported. The supported timeframes are: 1 minute, 5 minutes, 15 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, 1 day, 1 week, and 1 month.

7. The Pine Screener supports indicators that use request.security() and request.security_lower_tf() functions, with the following limitations: 

- These functions must only request data from the same symbol on which the indicator itself is calculated, which means that the value passed to the symbol parameter should be either syminfo.tickerid or an empty string.

- The requested timeframe must be in the list of the supported timeframes. The valid Pine string identifiers of these timeframes are: "1", "5", "15", "30", "60", "120", "240", "1D", "1W", and "1M".

8. You can scan only one screen at a time: if you already have a scan running in one tab, then another browser tab cannot run another scan.

9. The Pine Screener supports most input.*() functions and allows you to change values in these inputs via the “Settings” dialog. The following functions are not supported: input.timeframe(), input.symbol(), input.time(). If a script uses these input functions, the Pine Screener ignores the input value that the user selects, and uses its default value instead.

10. The indicator performs calculations on only the last 500 bars on the chart.

11. Using custom alert conditions is not compatible with scripts of Pine versions 3 and earlier. Using scripts of Pine v4 and higher is recommended.