Hi @adilet_akimshe,
After some tests I found that, although Qiskit technically allows you to create sessions in the free plan, in practice everything runs in job mode regardless, meaning that you could be waiting hours between consecutive iterations. 
This means that you can use qiskit_session as shown in this demo
from pennylane_qiskit import qiskit_session
...
with qiskit_session(dev) as session:
Or you can use Qiskit’s Session directly
from qiskit_ibm_runtime import Session
...
with Session(backend=backend, max_time='2h') as session:
But your jobs will still run separate from each other instead of all together.
Given the above, it’s probably best to avoid using sessions if you’re on the open plan.