Can a 1st generation Apple Pencil work with a iPad Pro 2020?

No. 2020 iPad Pro requires a second generation Pencil.

The first generation Pencil requires a Lightning port to both pair and charge the Pencil - an interface that the 2018/2020 iPad Pro doesn’t possess. The second generation Pencil uses a magnetic/inductive interface that docks to the edge of the iPad.

Apple Pencil (2nd generation)

You can use Apple Pencil (2nd generation) with these iPad models: 

• iPad Pro 12.9-inch (3rd generation) and later
• iPad Pro 11-inch (1st generation) and later

Apple Pencil (1st generation)

You can use Apple Pencil (1st generation) with these iPad models:

• iPad Pro 12.9-inch (1st or 2nd generation)
• iPad Pro 10.5-inch
• iPad Pro 9.7-inch
• iPad Air (3rd generation)
• iPad (7th generation)
• iPad (6th generation)
• iPad mini (5th generation)

Not sure which iPad you have? Identify your iPad model.

No.

You need the 2nd gen Apple Pencil.

Sorry.