If I keep using v3.x to develop and launch the app, do I need to replace the values of AppKey and AppSecret with those for v5.x?

No, you do not. The app developed based on App SDK v3.x still uses the key information including AppKey and AppSecret for v3.x. After you upgrade to v5.x, change the key information to that for v5.x.

To get the key information for v3.x and v4.x, perform the following steps:

1. Log in to theTuya IoT Development Platform.
2. Go toApp SDK>SDK Development.
3. Find the target SDK-based app and go to itsdetails page.
4. ClickSwitch to Old App SDK: v4in the top right corner of the page to switch to v4.x.

5. Then, you can get the key information for v4.x and v3.x.