Nobody will unlock a phone for free. Any mobile phone shop will unlock the handset - but they will charge for the service.
No. You can purchase the phone unlocked without any service plan, and connect it to any compatible carrier. It doesn't matter if the carrier is prepaid or not.
If you purchase the Samsung Galaxy S5 subsidized through a carrier, it's typically at $199 USD as of this writing. Unlocked, it can range from $550 to $799 USD.
It runs on the Verizon Network
Yes, the Samsung Galaxy S3 runs on Android 4.2, 4.3, or 4.4 depending on the carrier.
Unlocked versions of the Samsung Galaxy S5 have been around $660 USD or higher at the time of this writing. Subsidized or carrier-branded versions are around $199 USD.
Yes if you have wifi at home on the Galaxy Tab 3
no
There are a few variations on the Samsung Galaxy S3 that include 16, 32, and 64GB internal storage depending on the carrier.
If you purchase the Samsung Galaxy S5 subsidized through a carrier, it's typically at $199 USD as of this writing. Unlocked, it can range from $550 to $799 USD.
This depends on your carrier and plan. If you have no carrier, you may only make emergency calls.
Some of the Samsung phones currently available on Verizon include Samsung Galaxy S4, Samsung ATIV Odyssey, Samsung Galaxy Stratosphere II, Samsung Galaxy Note II, Samsung Galaxy S III, Samsung Galaxy Stellar. Samsung Brightside, Samsung Convoy 2 and Samsung Gusto 2.
The photo may be coming from a different carrier and that is the reason you must download the photo on a Samsung Galaxy S3.