Hi @mishal49,
if your interface (immersed boundary) is constantly changing (and if brute-force restarting every few time steps is not an option), then I am afraid it will be a bit complicated with preCICE at the moment, even if you directly call preCICE directly in your solver. @fsimonis and @DavidSCN are working on making this easier, but features in this direction will take a while till they are available.
I am not sure what you mean here. Using additional context from our previous communication, I assume that you want to use some of the features of the adapter (which?), without actually associating a specific OpenFOAM patch to the interface. This sounds very complicated, and I think it would be easier for you to just hard-code the preCICE calls into your solver. The source of the OpenFOAM adapter may look too long, but most of it is handling special cases and covers features which you may not need. For one specific case, it may be best to just hard-code.
By the way, I think that @KyleDavisSA tried to directly couple an immersed boundary solver in foam-extend a long time ago, without much success (if I remember correctly).
Other threads that may help: