No, there were no 4-bit consoles. The 2600 uses the 8-bit 6507 CPU and an 8-bit bus.

Yes, the 5200 was based around the 6502, one of the most famous 8-bit processors.

In fact, the 5200's internal hardware was almost identical to the Atari 400 and 800 ("8-bit family") computers. They made a few minor tweaks that meant games weren't directly compatible between the two, though.

8-bit is a surrounding of a video game e.g. Mega Man. 8-bit is from the Atari Computer System.

The lowest amount of bit a video game had was I believe 8-bit, on the Atari 2600.

Atari claimed that Atari Jaguar is the first 64 bit console. However, it in fact is not a true 64 bit console.

In reality, it was just two 32 bit chips stuck together, therefore not an actual 64 bit console.