 Here is a simplified Python script using PyAEDT for the given task. Please note that this script assumes you have the necessary permissions and environment set up for the tasks mentioned. Also, it's important to install the PyAEDT library before running the script.

```python
import os
import subprocess
import pyAEDT as aedt

# Set up project files and paths
project_path = "path/to/your/project"
temp_project_path = os.path.join(project_path, "temp_project")
edb_path = os.path.join(temp_project_path, "your_project.edb")
q3d_path = os.path.join(temp_project_path, "your_project.q3d")

# Download the project file
# (Replace 'your_project.prj' with the actual project file name)
subprocess.run(["aedt_download", f"{project_path}/your_project.prj", edb_path])

# Create a temporary project directory
os.makedirs(temp_project_path, exist_ok=True)

# Open EDB project
aedt.open(edb_path)

# Create a cutout on selected nets and export it to Q3D
# (Replace 'net1', 'net2' with the actual net names)
aedt.schematic.cutout.create(nets=['net1', 'net2'])
aedt.schematic.cutout.export(format='Q3D', file_name=q3d_path)

# Identify pin locations on the components and append Z elevation
# (Replace 'comp1', 'comp2' with the actual component names)
pin_locations = aedt.schematic.components.get_pins_locations(['comp1', 'comp2'])
z_elevation = 0.1  # Replace with the desired Z elevation

# Save and close the EDB
aedt.app.save()
aedt.app.quit()

# Open the EDB in Hfss 3D Layout to generate the 3D model
subprocess.run(["hfss3d", edb_path])

# Export the layout to Q3D
subprocess.run(["hfss3d", "-export", "-format", "Q3D", "-file", q3d_path])

# Launch the newly created Q3D project
subprocess.run(["q3d", q3d_path])

# Plot the project and assign sources and sinks on nets using the previously calculated positions
# (Replace 'net1', 'net2' with the actual net names)
# (Replace 'pin1', 'pin2' with the actual pin names)
# (Replace 'source_power', 'sink_power' with the actual source and sink power values)
subprocess.run(["q3d", "-plot", "-sources", f"net1,pin1,DC,source_power", f"net2,pin2,DC,sink_power"])

# Create a setup and a frequency sweep from DC to 2GHz
subprocess.run(["q3d", "-setup", "-frequency", "DC,2GHz"])

# Analyze the project, compute ACL and ACR solutions, plot them
subprocess.run(["q3d", "-analyze", "-acr", "-acl"])
subprocess.run(["q3d", "-plot", "-acr", "-acl"])

# Release the desktop
subprocess.run("taskkill /F /IM q3d.exe")
```

This script uses subprocess calls to run the AEDT, HFSS 3D Layout, and Q3D applications. Make sure to replace the placeholders with the actual project file names, net names, component names, pin names, and power values.