You can reinstall on the same or a new machine, but you must deactivate on the old machine first.
No. Classic licenses are version-locked.
To get SketchUp Pro 2025 or newer, you must purchase a subscription (no upgrade path exists for classic 2020). sketchup pro 2020 classic license key upd
However, you can run both on the same computer (e.g., keep 2020 for old projects, use subscription for new work). You can reinstall on the same or a
SketchUp Pro 2020 was the last version to support the "Classic" licensing scheme (Serial Number: TA-XXXXXXX). keep 2020 for old projects
In 2019, SketchUp (then owned by Trimble) announced that they were moving entirely to a Subscription Model. This meant that permanent licenses were no longer sold. However, users who owned valid Classic licenses were still able to use 2020.