4. If I don't convert to subscription, can I still use my perpetual license?

Yes. If your Qt licenses are perpetual, you may continue to use the product in perpetuity after your maintenance expires.  Access to product and technical support will only be available via the purchase of an Extended Maintenance Contract for software releases that are end-of-life. If you opt not to renew, please note that Qt will not guarantee to support software versions acquired with a perpetual license.

Please note, you will need a subscription license to access Qt 6.

Qt versions can be viewed here.