How much ml of lube it contain?

It will have 5ml of cube lubricant.

Which lube is best for moyo Rs3m 2021

You can use heavy lube like Calm/Nucleus for the core and Hurricane/Velocity for lubricating pieces.

I have a Moyu Meilong 3c 3x3 Should I buy the weight 3?

Weight 3 lubricant is suitable for both the pieces and core so you can lube your cube with it.

How long will 5-6 drops last on pieces?

It will last for a considerable 60-80 solves (approx). There is no fixed time frame as of how long the lube will last. It completely depends on how many solves you perform.

Does the calm lube slow the cube and does it last long?

Yes, it is much gummier weight 5 lubricant and it is suggested to be used on the core and springs.

How many times I can lube the cube with one syringe of hurricane?

One syringe contains around 90 drops of lube. However, it also depends upon the quantity you use at a time while lubing your cube. 
It is suggested to use 5-6 drops of lube in pieces at once.

Does cube lubricants expire? If yes, in how much time they can be expired

No, lubes never expire

Is the lube is good for a 3x3 magnetic cube

You can use this lube in any cube.

Can I use this lube for normal cube ?

Yes, you can use this lube in any cube.