What is the height of the coffee table when the top is not lifted?

The height of this coffee table is 18.5 inches when the top is not lifted.

Under "assembly required?" it just says "fully". Does that mean it comes fully assembled or the buyer fully assembles it? Just saying "fully" is too vague.

Yes, it is assembly required. You can check the installation guide: https://img2.homary.com/mall/file/2022/05/12/e104143c0e914870886a46f1c98c34a6.pdf

Could someone tell me the height of the table top once it is unfolded please?

The height of the table-top once it is unfolded is 66 cm

What is the level of assembly?

The level of assembly of the item is full assembly needed. You can check the isntallation guide: https://img2.homary.com/mall/file/2022/05/12/e104143c0e914870886a46f1c98c34a6.pdf or watch the install video in the product page.

Does this coffee table material made of pine wood?

This coffee table is made of MDF, without pine wood.

How many drawers the table have?

The coffee table has 3 drawers.

Does it include the small stools? If not, is there a similar lift-top coffee table with stools?

Sorry, this coffee table is not include the stools. The Similar lift top coffee table you may like: https://www.homary.com/item/5-pieces-lift-top-coffee-table-set-with-storage-convertible-dining-table-with-ottomans-42972.html