The best way to copy your keychains to a new computer is to export and then import them using Keychain Access. See Import and export keychain items.
However, you can also manually copy your keychains to another Mac/mac using the steps below. It should work in your scenario too.
On your Mac, locate the keychain files you want to transfer.
Keychains are ...
Some disks (like Transcent Jetdrive disks) need specific drivers and do not function under and OS older than 10.12.. Try and boot into the different options for recovery (like Command-R / Option-Command-R / Shift-Option-Command-R) and see if the disk is recognized in any of the versions.
Apple gear boots from external drives easily so you can always get a ...
The screenshot with the panic shows that the reason for the kernel panic was that launchd stopped running.
I would suggest looking at the log files for launchd to see if you can find the reason for that in there. Usually you'll see something like "exited at instruction [...]" or "trying to read/write [...]" or "[...] (sent by PID [...])" right before the ...
Two sites that are very Mac friendly are the iFixit site and the OWC (Other World Computing) site. OWC sells SSDs and many other Mac upgrades. I suggest you search the site for what you are looking for.
An iFixit example guide how to install a second HDD/SSD (with links where to buy all required parts and tools):
Installing MacBook Pro 15" Unibody Late ...
The usual result of removing the thermal sensor is roaring fans; I suspect that there's little reason for Apple to add some "if no drive, ignore sensor" logic, because Apple would want to replace the drive.
The best instructions for replacing components on your Mac can be found here:
Remember that your iMac ...
Apple uses a proprietary connector, which is usually described as a 12+16 pin PCIe connector. Or more simply "Mac SSD".
There are USB enclosures for these blades, though they tend to be very expensive - $70 to $100. Here's one:
However, note that this particular one claims not ...
You shouldn't get slower speeds because both SATA ports are SATA II (3Gb/s).
You can confirm this by going to About This Mac >> System Report. Then, go down to SATA/SATA Express and select the chipset controlling your optical drive.
(I don't have an optical drive for this example, unfortunately, so mine shows my SSD, but the concept is the same)
Look for ...
That model does not support SSD and HDD in addition to the optical
The 27” from 2010 does, however. It just needs a mounting bracket and the SSD. It’s SATA 3 Gbps bus and this link has lots of upgrade referrals: