There isn't any difference. They are the same products with the same ingredients, branded for different markets

The both products contain the same amount of selamectin which is 45 mg. in 0.75 ml liquid. Stronghold states 45 mg, Revolution states 60 mg / ml. Because there is 0.75 ml in the tube that makes 45 mg selamactin. Also we send don't send Stronghold if you order Revolution or vice versa. You get what you order.

Each tube contains 0.75 ml fluid. (45 mg. Selmectin)

Yes it is the original product manufactured by Pfizer and kills fleas, flea eggs and flea larvae.

This product doesn't kills mosquitoes. Advantix, Advantage Multi and Advantage are effective for mosquitoes.