PranavJadhav
I went ahead and patched a cache-invalidation bug for FreeFlarum forums, that will be officially fixed in the upcoming beta8.
PranavJadhav What is memory and storage allocated per instance?
That is dynamically allocated. There is, however, a limit of 2 concurrent PHP requests per forum (with backlog). In practice, this is enough for hundreds of simultaneous visitors.
PranavJadhav What if other instances come across high usage, will it affect mine?
Theoretically yes, but it hasn't happened so far. If it would happen (say, a forum becomes very popular), it would get moved to its own dedicated server.
Perhaps for paid premium plans, but there is no specific roadmap for that yet.
You can currently only change your custom domain, and download mysql data + avatars (from https://www.freeflarum.com/settings).
You cannot run custom SQL, or install your own extensions, as that would break the possibility for mass-maintenance. However, as all the popular extensions are installed, you normally won't require this. If there is anything though, get in touch at info@freeflarum.com and I'll see what I can do for you.