I am new to beyblades, I purchased a set of Takara Tomy burst beys from a guy who is getting out of it and I have a couple questions. 

Are some beyblades only right spin or only left spin? (the launcher I have seems to only be able to launch right spin beys, is there a way I can launch left or do I need to buy a special launcher?)

What determines the beyblades type? Is it the tip, middle layer, top layer, or all three?

Does the middle layer do anything important aside from add weight?

Most beyblades are only able to spin in either left or right direction. You will need a corresponding launcher for each direction, or get an LR launcher, which can launch in both directions

The beyblade parts type (attack-defense-stamina-balance) is usually deliberately categorized by Takara Tomy's advertising. For whole combo, I think the driver is the most prominent indicator to its type?

The disc mainly adds weight, but they also have other characteristics like weight distribution. Disks with more weight focused on the outside (OWD or Outer Weight Distribution) equals to better stamina but also higher burst risk in most cases.

Some disks also have slightly thicker tabs, which synergizes well with some layer gimmicks, particularly burst stoppers like Judgment or Lord.

Disks that are not compatible with frames (newer ones from GT mostly) have their own gimmick and unique shape.

Most beyblades are only able to spin in either left or right direction. You will need a corresponding launcher for each direction, or get an LR launcher, which can launch in both directions

The beyblade parts type (attack-defense-stamina-balance) is usually deliberately categorized by Takara Tomy's advertising. For whole combo, I think the driver is the most prominent indicator to its type?

The disc mainly adds weight, but they also have other characteristics like weight distribution. Disks with more weight focused on the outside (OWD or Outer Weight Distribution) equals to better stamina but also higher burst risk in most cases.

Some disks also have slightly thicker tabs, which synergizes well with some layer gimmicks, particularly burst stoppers like Judgment or Lord.

Disks that are not compatible with frames (newer ones from GT mostly) have their own gimmick and unique shape.

Very helpful, I figured out that one of my launchers can switch from right spin to left spin modes which is nice.

Are some beyblades only right spin or only left spin? (the launcher I have seems to only be able to launch right spin beys, is there a way I can launch left or do I need to buy a special launcher?)

Spriggan's or Spryzen's can spin both directions. (S3 and up) You need to buy a different launcher for Left. Either left spin or LR.

What determines the beyblades type? Is it the tip, middle layer, top layer, or all three?

Majority of the time tip or layer. Often though, if the parts don't add up (Attack tip and Stamina layer) It is a balance type.

Does the middle layer do anything important aside from add weight?

Agreed with eigerblade.

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Spoiler (Click to View)

Disks that are not compatible with frames (newer ones from GT mostly) have their own gimmick and unique shape.

Forgotten the pre-Core disks, have we? Lot more of them than core disks, though they're all pretty old and outclassed by now.

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Cincinnati-based Organizer, and owner of every single currently released TT Burst bey part in at least one color. Hard to think of anything I don't have from MFB either...

Disks that are not compatible with frames (newer ones from GT mostly) have their own gimmick and unique shape.

Forgotten the pre-Core disks, have we? Lot more of them than core disks, though they're all pretty old and outclassed by now.

Good catch LOL, but that's why I intentionally included the word "mostly". Although the older disk are more numerous, most of them are irrelevant and less common to find nowadays so I didn't bother mentioning them.