Hermes support for old javascript bundles

[mkondakov]

Description

We have project with non standard use of react-native. It's a main iOS application which can download react-native plugins from special store. It means that we have existed store with lot of already built react-native application in format of .jsbundle We try to switch from React-jsc to Hermes because some of 3rd-party dependencies, such as RNReanimated don't support React-jsc properly and already have switched to Hermes. We can see than old applications that were built with React-jsc are normally supported in iOS app that was built with Hermes. I didn't find any documentation how Hermes supports bundles that were built with React-jsc. And performance is not the main case in our project. Stability and backward compatibility are more important. But we periodically update react-native version to latest. And some libraries don't support React-jsc any more. So we have a dilemma, should we switch to Hermes or should we continue with React-jsc. I have few questions related to this topic:

1. Does Hermes fully supports older builds in format of javascript bundles. I see that in fact it supports older builds but I want to make sure that older builds are supported and will be supported.
2. Is it possible to build react-native app in format of javascript bundle with Hermes?
3. Is it possible to run few bundles in parallel? One in binary format and another in javascript format
4. Will newer version of react-native support binaries that were built with older Hermes version? (edited)