thought i did add a price. it's a 120 dollars.
Most, but not all of them can have firmware that low. You have to look at the serial number to know for sure if the 3ds will have <4.5 firmware.
link to the wiki that shows the serial numbers and models
Edit: Simple answer - it's not guaranteed that a regular 3ds will have 4.5 firmware.
CW7235xxxx is the highest.
These are the 3ds models/bundles released in the US that can come with compatible firmware:
Aqua Blue
Cosmo Black
Flame Red
Pearl Pink (bundled with Nintendogs + Cats)
Midnight Purple
Heroes of Ruin
The Legend of Zelda 25th Anniversary
Kingdom Hearts 3D: Dream Drop Distance
Fire Emblem Awakening
...but you still have to check the serial to be sure.
And the Flame Red and Aqua Blue 3ds are always 4.5 or below?Any 3ds with a serial number lower than that should work. The list just shows which colors/models were released before the 5.0 update.