iMac: stuck after internet recovery

I don't think your model can do a Network Restore. The computer did come with a set of installation DVDs. Use Disk 1 to install OS X 10.6.4. Upgrade that to 10.6.8. You can then access the App Store to download and install a later version of OS X.

Snow Leopard Erase and Install

1. Insert Snow Leopard DVD into the optical drive and restart the computer.
2. Immediately upon hearing the chime hold down the C key.
3. Release the key when the Apple logo appears and wait for the loading to finish.
4. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities' menu. After Disk Utility loads select the out-dented disk entry from the side list (mfgr.'s ID and drive size.) Click on the Partition tab in the Disk Utility’s right window. Set the number of partitions to one (1) from the drop down menu. Click on the Options button and select GUID, click OK button, set the format type to MacOS Extended, Journaled. Finally, click on the Apply button.
5. After formatting has finished quit Disk Utility. Continue with the OS X installation and follow the directions.
6. When the installation has finished the computer will restart into the Setup Assistant. After you complete the Setup Assistant you will be running a fresh installation of Snow Leopard.
7. Download and install Mac OS X 10.6.8 Update Combo v1.1.

I take it you did not partition and format the new SSD before installing.

Install Lion Through Yosemiteon a New HDD/SDD

Be sure you backup your files.

1. Restart the computer and after the chime press and hold down the Command-Option-R keys until a globe appears. Wait patiently - 5-15 minutes - until the Utility Menu appears.
2. Select Disk Utility from the Utility Menu and click on the Continue button.
3. After Disk Utility loads select the drive (usually, this is the out-dented entry with the mfgr.'s ID and size) from the side list. Click on the Erase tab in Disk Utility’s main window. A drop-down panel will appear.
4. Set the partition scheme to GUID then click. Set the Format type to Mac OS Extended (Journaled.) Click on the OK button and wait for the process to finish. Quit Disk Utility and return to the Utility Menu.
5. Select Install OS X from the Utility Menu and click on the Continue button.

This should install the version of OS X that came with the computer when it was new.

If you purchased it new and could do a Network Restore then you must have one of the later ones that had the firmware upgrade. I have a mid-2011 model in which I had to upgrade the firmware so it would do a Network Recovery.

I would have to guess that your repair may not have been done properly or the computer's problem was not due to a bad drive or you erred during the re-assembly. I don't think it's a PRAM battery. I've never replaced mine or even looked for one.

If the problem is the SSD you would need an external enclosure or a SATA to USB cable so you could try the SSD on a USB port. A SATA to USB cable can also be used on the HDD to test it without having to buy another enclosure.

How long did you wait after the screen switched to the Apple logo and spinning gear? I would allow up to 30 minutes just to be sure. Surprisingly, the process goes pretty slowly once it connects to the server.

I have these articles that could help. They are in dated order.

1. Mac OS X- Gray screen or prohibitory sign appears during startup
2. Tackle your Mac booting to a gray screen | MacIssues
3. Mac OS X- Gray screen appears during startup
4. How to Fix a Mac That Stalls on the Gray Screen at Startup
5. List Top 10 Troubleshooting Tips for Mac Startup Problems 10 troubleshooting tips for your Mac including blue or gray screen, safe boot, resetting the PRAM/NVRAM, question mark at boot, and other startup issues.