Hello

Allocation to the project and assignment to activities are two different things.
The project is a gateway. Allocation to this will give CRUD rights to people according to a profile on the elements of the project.
It can be a contact, a resource or even a user.
Assignment to activities only concerns resources. Those who will actually work on the activity.
It is therefore normal not to pass all the assignments on an activity.

Several accelerators can help you save time such as copying your activity by keeping assignments, you can also assign an entire team, an organization or even a pool of resources.

I am not asking for allocation to project,I was asking for status of project under assignment.If the project is in assigned state ,it means this project is in active state now,then all the activities under this project should also be assigned to concerned resources under those activities.Please let me know any info on this.

So it's always no.
There is no automatism on the projects.

ProjeQtOr is only a project management tool, it does not replace the project manager and will never make decisions for you.

It is not because you have 50 resources on your project that all these resources will work on one of your activities.
So no. Not all resources are transferred to activities. This work is to be done manually by you according to your needs for this activity.