How to find stocks that gain by 100%, for example, in a year?

You'd use the PctChange technical indicator for that.

Type PctChange into the search box on this forum for posts on the topic.

https://scan.stockcharts.com/search?Search=pctchange

Also type PctChange into the search at StockCharts.com and check out the Support articles

https://support.stockcharts.com/doku.php?id=scans:advanced_scan_syntax:pctchange_scans

A lot of good and great resources are available using the Search boxes.

As the indicators default to daily, you'd just need to add a modifier to the indicator. You can add "Weekly" and "Monthly" to most indicator scans to change the information that the scan engine looks at.

https://support.stockcharts.com/doku.php?id=faqs:how_do_i_create_a_scan_based_on_weekly_data